Discourse on Method

Descartes, Rene. Discourse on Method. Trans. Laurence J. Lafleur. New York: Macmillan, 1950.

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INTRODUCTION

DESCARTES’ PLACE IN HISTORY

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Descartes lived at a time of great changes. The mediaeval world was in the process of disintegration. The clergy had been divided for centuries into opposing factions following Thomas Aquinas, Duns Scotus, William of Occam, and others, and many individuals had been in practical revolt against the Church through an excessive interest in philosophy or science. Parts of the Church empire had fallen away through the rise of Protestantism, the Renaissance had recovered many of the ideas of Greek philosophy, exploration had stimulated interest in this world instead of the next, and the development of printing had disseminated knowledge much more widely than ever before.

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First, Descartes shared with many other individuals of his period a disbelief in authoritarianism and a belief in the unique adequacy of each individual’s reason for the discovery of truth.

…thus partly responsible for the decline of Roman Catholic authoritarianism, and for the development of anti-clericalism, particularly in France.

…supports Protestantism in its affirmation of the supremacy of the individual conscience, and is one of the principal sources of democratic theory. Locke, for instance, emphasized the democratic tendency of Descartes by eliminating innate ideas, the only source frorm which a supernatural ethic might arise. Hume accepted Locke’s ethical beliefs, and they were expanded into a coherent system of morality and political and economic theory by Bentham.

…America must be understood in the light of Locke’s ideas, modern England largely in terms of those of Bentham.

Second…Descartes’ rationalism and scientific optimism.

…philosophers over a period of two and a half centuries building systems which they are optimistically certain are close to the absolute truth. The task of science can also be accomplished, and the world thereby turned into a utopia: Descartes thought he might even achieve this result in his own lifetime.

…belief that science’s final success is just around the corner was characteristic of the modern period until late in the nineteenth century

…all laws must be universal, and eventually derivable from a single basic law of the universe.

…Newton combined Galileo’s laws of falling bodies with Kepler’s laws of planetary motions. But the first outstanding achievement in combining laws was that of Descartes himself when he combined the methods of algebra and geometry in the new field of analytic geometry.

…simultaneous discovery of the calculus by Leibniz and Newton, and on the calculus is based the whole superstructure of modern developments in mathematics and of its application to the understanding of nature.

The third field of Cartesian influence is the approach to philosophy through the analysis of experience.

Fourthly, Descartes’ proof of the existence of the self raised the question of what that certainly-existing self really is.

The fifth way in which Descartes was influential was in his expression of metaphysical dualism. This has become so thoroughly a part of our intellectual heritage that the man with no philosophical training whatsoever thinks along these lines, and finds the Cartesian philosophy obvious, to the extent that he may consider all other philosophies perverse distortions of the self evident truth.

…the explanation of how mind affected matter became more and more elaborate and indirect as scientific knowledge increased.

…basic assumption of science is that a necessary and sufficient cause can be found for any phenomenon. The conception held by science until very recently was that the necessary and sufficient cause would also be rational.

…modern science has developed with strong prejudices not only against Divine intervention in the natural order, but also against mental causes being efficacious in physical affairs.

…violent antipathy to mental telepathy, multiple personality, and hypnosis. More directly consequent upon the theory is the objection to telekinesis.

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Behaviorism is the natural consequence, and the redefinition of psychology in terms of stimulus-response, or organismic- environmental interrelationships.

…assumption that mental traits are not hereditary.

…all these prejudices are derived in part from Cartesian dualism, and that there is nothing in scientific theory or method, taken alone, to account for them.

…the resulting doctrine of materialism or epiphenomenalism…has been rendered meaningless by the developments in physics in the twentieth century.

…in the beginning God had willed it so.

…Deus ex machina…possible…denial that interaction occurs, so that the appearance of it is an illusion due to a perfect parallelism between the mental and the physical. This idea was developed by Leibniz.

…ontological level…denying dualism…neutral monism: the denial that matter and mind are different…Leibniz and Spinoza.

…more typical conclusion is that matter does not exist: Berkeley...

…Malebranche and Leibniz can be readily interpreted as idealists, and idealism soon became the most popular form of philosophy. Thus Descartes’ dualism let naturally both to the materialistic tendency in science and to the idealistic trend in philosophy.

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The sixth and last field in which Descartes; influence was prominent was epistemology.

First is the correspondence theory of truth, according to which at least some kinds of ideas are correct insofar as they are good copies of external reality. Second is a threefold source of knowledge…obtained intuitively…clear and distinct conceptions which must be true…

…scientific knowledge, not the acceptance of appearances…

…empirical data, are clearly another source of information…

….introspection and internal bodily feeling as well as the external senses…obtained from it by inference…

…eliminate…Descartes’ arguments for the existence of God, which involve a quite special problem…clear and distinct idea, always operates in terms of an immediate datum or in terms of inference…may be no more than two subdivisions of Descartes’ logical method. If this is not so, intuition becomes a mystical a priori and is just as dangerous in epistemology, and for the same reason, as the concept of a Deus ex machina is in metaphysics.

...Descartes’ correspondence theory, an idea could only be an adequate copy of another idea, never of the wholly different physical world, so that Berkeley’s subjective idealism is the logical result.

…ideas are also debarred from being copies of thinking beings or of God…

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Berkeley’s position must give way to the sceptical conclusions of Hume.

Locke provides a still more direct path to Hume’s scepticism: if all knowledge is sense data, then clearly we can have no knowledge of anything but sense data, and physical substance, mental substance, and logical rules must be outlawed. Finally, the problem thus posed, Hume’s solution to which is clearly unacceptable, leads to Kant, subsequent German idealism and the modern tendency to take problems of methodology, in science and philosophy, as prior to all other considerations.

DESCARTES AND SCIENCE

…Descartes thought of himself as a scientist at least as much as a philosopher or mathematician…

…customary to speak of Descartes’ scientific work as speculative and deductive, and to criticize him for failing to make more experiments and offer fewer unverified theories…unjustified.

…his empiricism has a rationalistic flavor that distinguishes it in two or three ways form that of the modern scientist.

…Church doctrine which, honestly or not, Descartes says is to be believed despite all reason and all evidence.

…some philosophical knowledge, or knowledge of universals, which is dependent only upon experience in general and not upon particular experiences…a priori and deductive…

… “appeared impossible to proceed further deductively,” and it would be necessary “to discover causes by their effects, and make use of many experiments.”

The second difference that we may discover between Cartesian and modern science lies in its logic.

…since all possible causes are readily perceived by us, the universe is rational as we are and scientific laws are precise, knowable, and recognizable, when discovered, as the best of all the possibilities…and hence inevitable.

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...no hint…of the recent conception of a scientific law that makes it a mere approximation to the truth, destined in the course of human investigation to be replaced by ever closer approximations.

…once the choice is made among the given possibilities, certainty has been achieved…

…that science has a finite task, and that it will be done in a short time. This was Bacon’s idea, and it persisted beyond the middle of the nineteenth century.

…Descartes was clearly the prince of optimists. He felt that he had contributed a considerable proportion of all possible knowledge, and had hopes of completing the job within his lifetime!

“Here is the Method,” he says in effect, “which I have discovered, and here, in Optics, Meteorology, and Geometry, are a few samples to show how successful this method has been in my hands. If you will invest in me, I can give you similar successes elsewhere; perhaps, in fine, the key to nature and human happiness.”

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Discourse on Method…outline…meditations on First Philosophy...

…Geometry…main stem of all modern mathematical development, but it was also the first important mathematical discovery since Greek times, and a stimulus to further thought in that field.

…specifically scientific…discourse on Method, Optics, and Meteorology...

…Optics…the statement of the wave theory of light; the vector analysis of motion; the law of sines in refraction; the first theoretical account of far-sightedness and near-sightedness; the first adequate account of space-perception; the first adequate account of the theory of lenses; the first recognition of spherical aberration and of the method of correcting it; the determination of light-gathering power in a telescope; the principle of he iris diaphragm; the draw-tube; the telescopic finder; the use of illuminating equipment in conjunction with the microscope; and the parabolic mirror.

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…Meteorology…rejects Divine intervention as the explanation of events; he states the kinetic theory of heat, and foreshadows Charles’s law, and the concept of specific heat; he gives the first outline of a scientific meteorology in his treatment of winds, clouds, and precipitation; he gives a correct and accurate description and explanation for the primary, secondary, and reflection rainbows; and he describes the division of white light into colors by a prism, and sets up the apparatus of the slit spectroscope.

DESCARTES AND RELIGION

Descartes accepts the existence of God, adduces proofs of his existence, and bases his whole philosophy upon God. God not only created mind and matter in the beginning, but is continuously responsible for their continued existence.

…theological doctrines are to be considered exempt from his general doubt…

The opposite hypothesis that Descartes was essentially atheistic, may be argued with greater plausibility…

…he is forced to introduce God into his system, proving his existence by arguments taken over from the Mediaeval theologians, and assigning to God such tasks as do not interfere with the essential Cartesian philosophy.

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First, I know of my own existence with absolute certainty; secondly, since I know one thing without inferring it from anything else, there must be a method of knowledge other than inference, and this must depend upon the clarity and distinctness of the idea; thirdly, since I possess clear and distinct ideas of both physical and mental things, these must exist. Descartes inserts between the second and third steps a sort of parenthesis in which it is argued (a), that he second step itself might be mistaken if the world were run by a malicious demon; (b), an infinitely good God exists; and (c), suggestion (a) is therefore wrong and the second step of the original argument is confirmed. The hypothesis that Descartes’ discussion of the existence of God is insincere is thus borne out by a number of considerations arising from its character and its position in the total argument.

…today to recognize Descartes’ genius; so were most of his contemporaries, and Descartes himself is clearly in full agreement…

…juxtaposition of mock modesty with what would doubtless be called braggadocio…

We cannot understand as serious his exemption of Church doctrine from doubt, at a stage in his argument (Part Three) when even the existence of God is being questioned.

…attempt to hedge Galileo’s fatal belief that the earth travels around the sun that it might not be taken as heretical by the Church: to do this he achieved something like a primitive doctrine of he relativity of motion.

…due to policy rather than to philosophy.

Whenever Descartes acknowledges the infallibility of the Church, or its right to control his thoughts, there is an unmistakable flavor of irony present…

LAURENCE J. LAFLEUR

DISCOURSE ON THE METHOD OF RIGHTLY CONDUCTING THE REASON AND SEEKING TRUTH IN THE SCIENCES

…may be divided into six parts. In the first will be found various thoughts on the sciences; in the second, the principal rules of the method the author has used; in the third, some moral rules derived form this method; in the fourth, his proofs of the existence of God and of the human soul which form the basis of his philosophy; in the fifth are treated some questions of physics, especially the explanation of the heartbeat and of some other difficulties in medicine, as well as the difference between the souls of men and animals; and in the last, some prerequisites for further advances in the study of nature, as well as the author’s reasons for writing this work.

PART ONE

SOME THOUGHTS ON THE SCIENCES

I know how subject we are to making false judgments in things that concern ourselves, and how much we ought to mistrust the judgments of our friends when they are in our own favor. But I should be glad to show in this Discourse what are the paths I have taken, and to present a sketch of my life, so that each one can form his own judgment of it.

From my childhood I lived in world of books, and since I was taught that by their help I could gain a clear and assured knowledge of everything useful in life, I was eager to learn from them.

All this led me to conclude that I could judge others by myself, and to decide that there was no such wisdom in the world as I had previously hoped to find.

…the languages which one learns there are necessary to understand the works of the ancients; and that the delicacy of fiction enlivens the mind; that famous deeds of history ennoble it and, if read with understanding, aid in maturing one’s judgment; that the reading of all the great books is like conversing with the best people of earlier times.

…philosophy teaches us to talk with an appearance of truth about all things, and to make ourselves admired by the less learned;…

For conversing with the ancients is much like traveling. It is good to know something of the customs of various peoples, in order to judge our own more objectively…

…histories, if they do not alter or embroider episodes to make them more worth reading, almost always omit the meanest and least illustrious circumstances so that the remainder is distorted.

I was especially pleased with mathematics, because of the certainty and self-evidence of its proofs…

I compared the ethical writings of the ancient pagans to very superb and magnificent palaces built only on mud and sand: they laud the virtues and make them appear more desirable than anything else in the world; but they give no adequate criterion of virtue, and often what they call by such a name is nothing but apathy, parricide, pride or despair.

…the truths of revelation which lead thereto are beyond our understanding, I would not have dared to submit them to the weakness of my reasonings.

…philosophy…studied for many centuries by the most outstanding minds without having produced anything which is not in dispute…

…when I noticed how many different opinions learned men may hold on the same subject, despite the fact that no more than one of them can ever by right, I resolved to consider almost as false any opinion which was merely plausible.

…I knew enough of the disreputable doctrines not to be taken in by the promises of an alchemist, the predictions of an astrologer, the impostures of a magician, or by the tricks and boasts of any of those who profess to know that which they do not know.

…I might find much more of the truth in the cogitations which each man made on things which were important to him, and where he would be the loser if he judged badly, than in the cogitations of a man of letters in his study, concerned with speculations which produce no effect…

…just about as much difference of opinion as I had previously remarked among philosophers.

…I became acquainted with customs generally approved and accepted by other great peoples that would appear extravagant and ridiculous among ourselves, and so I learned not to believe too firmly what I learned only from example and custom.

PART TWO

THE PRINCIPAL RULES OF THE METHOD

…those ancient towns which were originally nothing but hamlets, and in the course of time have become great cities, are ordinarily very badly arranged compared to one of the symmetrical metropolitan districts which a city planner has laid out on an open plain according to his own designs.

…peoples who were once half savage, and who became civilized by a gradual process and invented their laws one by one as the harmfulness of crimes and quarrels forced them to outlaw them, would be less well governed than those who have followed the constitutions of some prudent legislator from the time that their communities were founded.

…the sciences found in books, at least those whose reasons were only probable and which had no proofs, have grown up little by little by the accumulation of the opinions of many different persons, and are therefore by no means as near to the truth as the simple and natural reasonings of a man of good sense concerning the things which he experiences.

It is therefore impossible that our judgments should be as pure and firm as they would have been had we the whole use of our reason from the time of our birth and if we had never been under any other control.

…a private individual should not seek to reform a nation by changing all its customs and destroying it to construct it anew, nor to reform the body of knowledge or the system of education…as far as the opinions which I had been receiving since my birth were concerned, I could not do better than to reject them completely…

…I would succeed in conducting my life much better than if I built only upon the old foundations…and gave credence to the principles which I had acquired in my childhood without ever having examined them to see whether they were true or not.

…many institutions have defects…

...custom has perhaps even found ways to avoid or correct more defects than prudence could have done.

…proposing some new reform…I would be loath to permit it to be published. Never has my intention been more than to try to reform my own ideas…

…those who think themselves more able than they really are…once they have taken the liberty of doubting their established principles, thus leaving the highway, they will never be able to keep to the narrow path which must be followed to go more directly, and will remain lost all their lives…

…in my travels I had found that those who held opinions contrary to ours were neither barbarians nor savages, but that many of them were at least as reasonable as ourselves.

…the same man, with the same capacity for reason, becomes different as a result of being brought up among Frenchmen or Germans than he would be if he had been brought up among Chinese or cannibals…in our fashions, the thing which pleased us ten years ago and perhaps will please us again ten years in the future, now seems extravagant and ridiculous.

…anything somewhat difficult to discover, since it is much more likely that a single man will have discovered it than a whole people…

…I was thus constrained to embark on the investigation for myself.

…I had, when younger, studied logic, and among those of mathematics, geometrical analysis and algebra…should be able to contribute something to my design…

…I thought that some other method must be found to combine the advantages of these three and to escape their faults…just as the multitude of laws frequently furnishes an excuse for vice, and a state is much better governed with a few laws which are strictly adhered to…the four following…not to violate them even in a single instance.

…first…never to accept anything as true unless I recognized it to be evidently such…

…it presented itself so clearly and distinctly to my mind that there was no occasion to doubt it.

…second…to divide each of the difficulties which I encountered into as many parts as possible…

…third…to think in an orderly fashion beginning with the things which were simplest and easiest to understand, and gradually and by degrees reaching toward more complex knowledge…

…last…to make enumerations so complete, and reviews so general, that I would be certain that nothing was omitted.

…long chains of reasoning…simple and easy which enabled the geometricians to reach the most difficult demonstrations…

…carefully follow the order necessary to deduce each one from the others…there cannot be any propositions so abstruse that we cannot prove them, or so recondite that we cannot discover them.

…begins with the simplest and easiest to know.

…although the objects they discuss are different, all these branches are in agreement in limiting their consideration of the relationships or proportions between their various objects. I judged therefore that it would be better to examine these proportions in general, and use particular objects as illustrations only in order to make their principles easier to comprehend…

…I could consider them better singly as relationships between lines…

..when taken in groups, I had to express them in numbers…

Thus I took the best traits of geometrical analysis and algebra, and corrected the faults of one by the other.

…each truth that I found was a rule which helped me to find others, so that I not only solved many problems which I had previously judged very difficult…I could determine to what extent a still-unsolved problem could be solved, and what procedures should be used in solving it.

…there is only one true solution to a given problem…

…a child who has learned arithmetic and had performed an addition according to the rules may feel certain that as far as that particular sum is concerned, he has found everything that the human mind can discover.

…I had observed that all the basic principles of the sciences were taken from philosophy, which itself had no certain ones. It therefore seemed that I should first attempt to establish philosophic principles…

…preparation would consist partly in freeing my mind from the false opinions which I had previously acquired, partly in building up a fund of experiences which should serve afterwards as the raw material for my reasoning, an partly in training myself in the method which I had determined upon…

PART THREE

SOME MORAL RULES DERIVED FROM THE METHOD

We must see that we are provided with a comfortable place to stay while the work of rebuilding is going on.

…I prepared a provisional code of morality for myself, consisting of three or four maxims which I here set forth.

…first…to obey the laws and customs of my country, constantly retaining the religion in which, by God’s grace, I had been brought up since childhood…

While there may be, no doubt, just as reliable persons among the Persians or the Chinese as among ourselves, it seemed more practical to pattern my conduct on that of the society in which I would have to live.

…to learn people’s true opinions, I should pay attention to their conduct rather than to their words…

…many are not aware of their own beliefs, since the mental process of knowing a thing is distinct from, and can occur without, the mental process of knowing that we know it.

…second…to be as firm and determined in my actions as I could be, and not to act on the most doubtful decisions, once I had made them, any less resolutely than on the most certain.

…third…always to seek to conquer myself rather than fortune, to change my desires rather than the established order, and generally to believe that nothing except our thoughts is wholly under our control…

After thus assuring myself of these maxims, and having put them aside with the truths of the Faith, which have always been most certain to me, I judged that I could proceed freely to reject all my other beliefs.

In the nine years that followed I wandered here and there throughout the world, trying everywhere to be spectator rather than actor in all the comedies that go on.

…I tried to clear my mind of all the errors that previously accumulated. In this I did not wish to imitate the sceptics, who doubted only for the sake of doubting and intended to remain always irresolute; on the contrary, my whole purpose was to achieve greater certainty and to reject the loose earth and sand in favor of rock and clay.

…I encountered nothing that did not lead me to some certain conclusions, even if it were only that the matter was wholly uncertain.

…I set aside a few hours now and then for practice upon mathematical difficulties.

…rejecting those principles of the sciences in question which I did not find sufficiently well established…

…I never desisted from my design and continued to achieve greater acquaintance with truth, perhaps more than I would have if I had only read books or sought the society of men of letters.

…I reached my decision about the difficulties ordinarily in dispute among the learned…

…I sought to lay the groundwork of a philosophy more certain than popular belief.

PART FOUR

PROOF OF THE EXISTENCE OF GOD AND OF THE HUMAN SOUL

…I decided to suppose that nothing that had ever entered my mind was more real than the illusions of my dreams…it was necessarily true that who thought so was something. Since this truth, I think, therefore I am, was so firm and assured that all the most extravagant suppositions of he sceptics were unable to shake it, I judged that I could safely accept it as the first principle of the philosophy I was seeking.

…I could imagine that I had no body, and that there was no world nor any place that I occupied…

…from the very fact that I doubted the truth of other things, it followed very evidently and very certainly that I existed. On the other hand, if I had ceased to think while all the rest of what I had ever imagined remained true, I would have had no reason to believe that I existed; therefore I concluded that I was a substance whose whole essence or nature was only to think, and which, to exist, has no need of space nor of any material thing. Thus it follows that this ego, this soul, by which I am what I am, is entirely distinct from the body…

…even if the body were not the soul would not cease to be all that it now is.

Next I considered in general what is required of a proposition for it to be true and certain…

…nothing at all in this statement, “I think, therefore I am,” to assure me that I was saying the truth, unless it was that I saw very clearly that to think one must exist.

…general rule that … very clearly and very distinctly are always true…

…difficulty in deciding which are those which we conceive distinctly.

…I saw clearly that it was a greater perfection to know than to doubt.

…source I had learned to think of something more perfect than myself, and it appeared evident that it must have been from some nature which was in fact more perfect.

…sky, earth, light, heat…nothing in them superior to my own nature.

…it is no less repugnant to good sense to assume what is more perfect comes from and depends on the less perfect than it is to assume that something comes from nothing…

…this idea was put in my mind by a nature that was really more perfect than I was…

…I saw that doubt, inconstancy, sorrow and similar things could not be part of God’s nature, since I would be happy to be without them myself.

…intelligent nature is distinct from corporeal nature, I considered that composition is an evidence of dependency and that dependency is manifestly a defect. From this I judged that it could not be a perfection in God to be composed of these two natures…

At this point I wished to seek for other truths, and proposed for consideration the object of the geometricians…a continuous body, or a space infinitely extended in length, breadth, and height or depth; divisible into various parts which can have different shapes and sizes and can be moved or transposed in any way.

…certainty which everyone attributes to them is only based on the fact that they are evidently conceived, following the rule previously established…nothing at all in them to assure me of the existence of their object…

When I turned back to my idea of a perfect Being, on the other hand, I discovered that existence was included in that idea in the same way that the idea of a triangle contains the equality of its angles.

…it is at least as certain that God, who is this perfect Being, exists, as any theorem of geometry could possibly be.

…philosophers hold it as a maxim in the schools that there is nothing in the understanding which was not first in the senses, a location where it is clearly evident that the ideas of God and of the soul have never been.

…neither our imagery nor our senses could assure us of anything without the co-operation of our understanding.

How could one know that the thoughts which come to us in dreams are false rather than the others, since they are often no less vivid and detailed?

…all those things which we conceived very clearly and very distinctly are true, is known to be true only because God exists, and because he is a perfect Being, and because everything in us comes from him.

…though we often have ideas which contain falsity, they can only be those ideas which contain some confusion and obscurity, in which respect hey participate in nothingness.

…if we did not know that all reality and truth with us came form a perfect and infinite Being, however clear and distinct our ideas might be, we would have no reason to be certain that they were endowed with the perfection of being true.

PART FIVE

SOME QUESTIONS OF PHYSICS

I intended to include in it all that I thought I knew, before writing it, concerning the nature of material things. But I found myself in the same state as painters, who cannot equally well represent in a two-dimensional painting all the various faces of a solid body... and so choose one to bring to the light, and leave the others in shadow, so that they can be seen only while viewing the selected side. Therefore, fearing that I would not be able to put into any discourse all that I intended, I undertook solely to describe a length what I thought on the subject of light, and took that occasion to add something concerning the sun and the fixed stars, since they are almost the only sources of light; of the sky, since it transmits it; of the planets, the comets, and earth, since they reflect it; and in particular of all the objects on earth, since they are either colored or transparent or luminous; and finally of man, since he is the observer of it.

I therefore resolved to leave this world for them to dispute about, and to speak only of what would happen in a new one, if God should now create, somewhere in imaginary space, enough matter to make one; and if he agitated the various parts of this matter without order, making a chaos as confused as the poets could imagine, but that afterward he did nothing but lend his usual support to nature, allowing it to behave according to the laws he had established.

…I tried to demonstrate everything which might be doubtful, and to show that nature is such that even if God had created several worlds, there would have been none where these laws were not observed.

…light, I explained at considerable length its nature when contained in the sun and the stars, how from hither it traverses in an instant the immense reaches of the heavens and how it is reflected from the planets and comets toward the earth…

…substance, situation, movements, and all the diverse qualities of these celestial objects and stars.

Thence I went on to speak particularly of the earth: how, even though I had expressly supposed that God had given no weight to the matter of which it was composed, all its parts would tend exactly toward its center; how the disposition of the celestial bodies and stars, principally the moon, would cause an ebb and flow in the water and air on its surface, similar in all respects to the tides of our seas…

…whole of the nature of fire…

Examining the functions which such a body would have, I discovered everything that can exist without thinking; everything except that which is contributed by the soul: that part of us distinct from the body whose essence, as we have previously said, is only to think. These functions are the same as those in which the unreasoning animals resemble us, and do not include any of those which are dependent on thinking and which belong to us as men. These human qualities I discovered somewhat later, when I supposed that God created a rational soul and joined it to the body in a certain fashion which I described.

…the heart of an animal with lungs is quite similar to that of man…

…the motion which I have just explained follows necessarily from the mere disposition of the parts of the heart visible to the naked eye, from the heat which one can feel with the fingers, and from the nature of the blood, which one can learn by experiment…

This will hardly seem strange to those who know how many automata or machines can be made by human industry, although these automata employ very few parts in comparison to the large number of bones, muscles, nerves, arteries, veins, and all the other component parts of each animal. Such persons will therefore think of this body as a machine created by the hand of God, and in consequence incomparably better designed and with more admirable movements than any machine that can be invented by man.

…that a machine could be so made that it would utter words, and even words appropriate to physical acts which cause some change in its organs; as, for example, if it was touched in some spot that it would ask what you wanted to say to it; if in another, that it would cry that it was hurt, and so on for similar things. But it could never modify its phrases to reply to the sense of whatever was said in its presence, as even the most stupid men can do.

By these two methods we can also recognize the difference between man and animals. For it is a very remarkable thing that there are no men, not even the insane, so dull and stupid that they cannot put words together in a manner to convey their thoughts. On the contrary, there is no other animal , however perfect and fortunately situated it may be, that can do the same.

Actually, when we know how different they are, we understand more fully the reasons which prove that our soul is by nature entirely independent of the body, and consequently does not have to die with it. Therefore, as long as we see no other causes which might destroy it, we are naturally led to conclude that it is immortal.

PART SIX

SOME PREREQUISITES FOR FURTHER ADVANCES IN THE STUDY OF NATURE

Three years ago, when I had completed the treatise containing all these matters, and when I was beginning to review it for purposes of publication, I learned that people to whom I defer, an whose authority over my actions is hardly less than that of my own reason over my thoughts, had disapproved of a hypothesis in the field of physics that had been published somewhat earlier by another person.

…instead of the speculative philosophy now taught in the schools we can find a practical one, by which, knowing the nature and behavior of fire, water, air, stars, the heavens, and all the other bodies which surround us, as well as we now understand the different skills of our workers, we can employ these entities for all the purposes for which they are suited, and so make ourselves masters and possessors of nature.

…we might rid ourselves of an infinity of maladies of body as well as of mind, and perhaps also of the enfeeblement of old age, if we had sufficient understanding of the causes and of all the remedies which nature has provided. It was my intention to devote my whole life to the pursuit of this much-needed service…

…I first tried to discover the general principles of first causes of all that exists or could exist in the world without taking any causes into consideration but God as creator, and without using any evidence save certain indications of the truth which we find in our own minds. After that I examined what were the first and commonest effects which could be deduced from these causes; and it seems to me that by this procedure I discovered skies, stars, and earth, and even, on the earth, water, air fire, minerals...

…infinity of others which might have been there if God had so willed. It thus appeared impossible to proceed further deductively, and if we were to understand and make use of things, we would have to discover causes by their effects, and make use of many experiments.

…I hoped to show so clearly how useful my project might be that I would oblige all those who desire human benefit, all those who are truly virtuous and not merely so in affectation or reputation, both to communicate to me the experiments that they have already made and to assist me in the prosecution of what remained to be done.

…and if my writings have any value, those into whose hands they fall after my death may use them as may be most appropriate. But I decided that I should never consent to have them published during my life, for fear that the opposition and controversy which they might arouse, and the reputation which they might possibly bring me, would cause me to waste time which I plan to use in research.

Discourse on the Method of Rightly Conducting the Reason, and Seeking Truth in the Sciences

by Rene Descartes

Preface

If this Discourse appear too long to be read at once, it may be divided into six Parts: and, in the first, will be

found various considerations touching the Sciences; in the second, the principal rules of the Method which the

Author has discovered, in the third, certain of the rules of Morals which he has deduced from this Method; in the

fourth, the reasonings by which he establishes the existence of God and of the Human Soul, which are the

foundations of his Metaphysic; in the fifth, the order of the Physical questions which he has investigated, and, in

particular, the explication of the motion of the heart and of some other difficulties pertaining to Medicine, as also

the difference between the soul of man and that of the brutes; and, in the last, what the Author believes to be

required in order to greater advancement in the investigation of Nature than has yet been made, with the

reasons that have induced him to write.

Chapter 1

Good sense is, of all things among men, the most equally distributed; for every one thinks himself so abundantly

provided with it, that those even who are the most difficult to satisfy in everything else, do not usually desire a

larger measure of this quality than they already possess. And in this it is not likely that all are mistaken; the

conviction is rather to be held as testifying that the power of judging aright and of distinguishing truth from error,

which is properly what is called good sense or reason, is by nature equal in all men; and that the diversity of our

opinions, consequently, does not arise from some being endowed with a larger share of reason than others, but

solely from this, that we conduct our thoughts along different ways, and do not fix our attention on the same

objects. For to be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it. The

greatest minds, as they are capable of the highest excellences, are open likewise to the greatest aberrations;

and those who travel very slowly may yet make far greater progress, provided they keep always to the straight

road, than those who, while they run, forsake it.

For myself, I have never fancied my mind to be in any respect more perfect than those of the generality; on the

contrary, I have often wished that I were equal to some others in promptitude of thought, or in clearness and

distinctness of imagination, or in fullness and readiness of memory. And besides these, I know of no other

qualities that contribute to the perfection of the mind; for as to the reason or sense, inasmuch as it is that alone

which constitutes us men, and distinguishes us from the brutes, I am disposed to believe that it is to be found

complete in each individual; and on this point to adopt the common opinion of philosophers, who say that the

difference of greater and less holds only among the accidents, and not among the forms or natures of

individuals of the same species.

I will not hesitate, however, to avow my belief that it has been my singular good fortune to have very early in life

fallen in with certain tracks which have conducted me to considerations and maxims, of which I have formed a

method that gives me the means, as I think, of gradually augmenting my knowledge, and of raising it by little and

little to the highest point which the mediocrity of my talents and the brief duration of my life will permit me to

reach. For I have already reaped from it such fruits that, although I have been accustomed to think lowly enough

of myself, and although when I look with the eye of a philosopher at the varied courses and pursuits of mankind

at large, I find scarcely one which does not appear in vain and useless, I nevertheless derive the highest

satisfaction from the progress I conceive myself to have already made in the search after truth, and cannot help

entertaining such expectations of the future as to believe that if, among the occupations of men as men, there is

any one really excellent and important, it is that which I have chosen.

After all, it is possible I may be mistaken; and it is but a little copper and glass, perhaps, that I take for gold and

diamonds. I know how very liable we are to delusion in what relates to ourselves, and also how much the

judgments of our friends are to be suspected when given in our favor. But I shall endeavor in this discourse to

describe the paths I have followed, and to delineate my life as in a picture, in order that each one may also be

able to judge of them for himself, and that in the general opinion entertained of them, as gathered from current

report, I myself may have a new help towards instruction to be added to those I have been in the habit of

employing.

My present design, then, is not to teach the method which each ought to follow for the right conduct of his

reason, but solely to describe the way in which I have endeavored to conduct my own. They who set themselves

to give precepts must of course regard themselves as possessed of greater skill than those to whom they

prescribe; and if they err in the slightest particular, they subject themselves to censure. But as this tract is put

forth merely as a history, or, if you will, as a tale, in which, amid some examples worthy of imitation, there will be

found, perhaps, as many more which it were advisable not to follow, I hope it will prove useful to some without

being hurtful to any, and that my openness will find some favor with all.

From my childhood, I have been familiar with letters; and as I was given to believe that by their help a clear and

certain knowledge of all that is useful in life might be acquired, I was ardently desirous of instruction. But as soon

as I had finished the entire course of study, at the close of which it is customary to be admitted into the order of

the learned, I completely changed my opinion. For I found myself involved in so many doubts and errors, that I

was convinced I had advanced no farther in all my attempts at learning, than the discovery at every turn of my

own ignorance. And yet I was studying in one of the most celebrated schools in Europe, in which I thought there

must be learned men, if such were anywhere to be found. I had been taught all that others learned there; and not

contented with the sciences actually taught us, I had, in addition, read all the books that had fallen into my hands,

treating of such branches as are esteemed the most curious and rare. I knew the judgment which others had

formed of me; and I did not find that I was considered inferior to my fellows, although there were among them

some who were already marked out to fill the places of our instructors. And, in fine, our age appeared to me as

flourishing, and as fertile in powerful minds as any preceding one. I was thus led to take the liberty of judging of

all other men by myself, and of concluding that there was no science in existence that was of such a nature as I

had previously been given to believe.

I still continued, however, to hold in esteem the studies of the schools. I was aware that the languages taught in

them are necessary to the understanding of the writings of the ancients; that the grace of fable stirs the mind;

that the memorable deeds of history elevate it; and, if read with discretion, aid in forming the judgment; that the

perusal of all excellent books is, as it were, to interview with the noblest men of past ages, who have written

them, and even a studied interview, in which are discovered to us only their choicest thoughts; that eloquence

has incomparable force and beauty; that poesy has its ravishing graces and delights; that in the mathematics

there are many refined discoveries eminently suited to gratify the inquisitive, as well as further all the arts an

lessen the labour of man; that numerous highly useful precepts and exhortations to virtue are contained in

treatises on morals; that theology points out the path to heaven; that philosophy affords the means of

discoursing with an appearance of truth on all matters, and commands the admiration of the more simple; that

jurisprudence, medicine, and the other sciences, secure for their cultivators honors and riches; and, in fine, that

it is useful to bestow some attention upon all, even upon those abounding the most in superstition and error, that

we may be in a position to determine their real value, and guard against being deceived.

But I believed that I had already given sufficient time to languages, and likewise to the reading of the writings of

the ancients, to their histories and fables. For to hold converse with those of other ages and to travel, are almost

the same thing. It is useful to know something of the manners of different nations, that we may be enabled to

form a more correct judgment regarding our own, and be prevented from thinking that everything contrary to our

customs is ridiculous and irrational, a conclusion usually come to by those whose experience has been limited

to their own country. On the other hand, when too much time is occupied in traveling, we become strangers to

our native country; and the over curious in the customs of the past are generally ignorant of those of the present.

Besides, fictitious narratives lead us to imagine the possibility of many events that are impossible; and even the

most faithful histories, if they do not wholly misrepresent matters, or exaggerate their importance to render the

account of them more worthy of perusal, omit, at least, almost always the meanest and least striking of the

attendant circumstances; hence it happens that the remainder does not represent the truth, and that such as

regulate their conduct by examples drawn from this source, are apt to fall into the extravagances of the

knight-errants of romance, and to entertain projects that exceed their powers.

I esteemed eloquence highly, and was in raptures with poesy; but I thought that both were gifts of nature rather

than fruits of study. Those in whom the faculty of reason is predominant, and who most skillfully dispose their

thoughts with a view to render them clear and intelligible, are always the best able to persuade others of the truth

of what they lay down, though they should speak only in the language of Lower Brittany, and be wholly ignorant of

the rules of rhetoric; and those whose minds are stored with the most agreeable fancies, and who can give

expression to them with the greatest embellishment and harmony, are still the best poets, though unacquainted

with the art of poetry.

I was especially delighted with the mathematics, on account of the certitude and evidence of their reasonings;

but I had not as yet a precise knowledge of their true use; and thinking that they but contributed to the

advancement of the mechanical arts, I was astonished that foundations, so strong and solid, should have had no

loftier superstructure reared on them. On the other hand, I compared the disquisitions of the ancient moralists to

very towering and magnificent palaces with no better foundation than sand and mud: they laud the virtues very

highly, and exhibit them as estimable far above anything on earth; but they give us no adequate criterion of

virtue, and frequently that which they designate with so fine a name is but apathy, or pride, or despair, or

parricide.

I revered our theology, and aspired as much as any one to reach heaven: but being given assuredly to

understand that the way is not less open to the most ignorant than to the most learned, and that the revealed

truths which lead to heaven are above our comprehension, I did not presume to subject them to the impotency of

my reason; and I thought that in order competently to undertake their examination, there was need of some

special help from heaven, and of being more than man.

Of philosophy I will say nothing, except that when I saw that it had been cultivated for many ages by the most

distinguished men, and that yet there is not a single matter within its sphere which is not still in dispute, and

nothing, therefore, which is above doubt, I did not presume to anticipate that my success would be greater in it

than that of others; and further, when I considered the number of conflicting opinions touching a single matter that

may be upheld by learned men, while there can be but one true, I reckoned as well-nigh false all that was only

probable.

As to the other sciences, inasmuch as these borrow their principles from philosophy, I judged that no solid

superstructures could be reared on foundations so infirm; and neither the honor nor the gain held out by them

was sufficient to determine me to their cultivation: for I was not, thank Heaven, in a condition which compelled

me to make merchandise of science for the bettering of my fortune; and though I might not profess to scorn glory

as a cynic, I yet made very slight account of that honor which I hoped to acquire only through fictitious titles. And,

in fine, of false sciences I thought I knew the worth sufficiently to escape being deceived by the professions of an

alchemist, the predictions of an astrologer, the impostures of a magician, or by the artifices and boasting of any

of those who profess to know things of which they are ignorant.

For these reasons, as soon as my age permitted me to pass from under the control of my instructors, I entire y

abandoned the study of letters, and resolved no longer to seek any other science than the knowledge of myself,

or of the great book of the world. I spent the remainder of my youth in traveling, in visiting courts and armies, in

holding intercourse with men of different dispositions and ranks, in collecting varied experience, in proving

myself in the different situations into which fortune threw me, and, above all, in making such reflection on the

matter of my experience as to secure my improvement. For it occurred to me that I should find much more truth

in the reasonings of each individual with reference to the affairs in which he is personally interested, and the

issue of which must presently punish him if he has judged amiss, than in those conducted by a man of letters in

his study, regarding speculative matters that are of no practical moment, and followed by no consequences to

himself, farther, perhaps, than that they foster his vanity the better the more remote they are from common

sense; requiring, as they must in this case, the exercise of greater ingenuity and art to render them probable. In

addition, I had always a most earnest desire to know how to distinguish the true from the false, in order that I

might be able clearly to discriminate the right path in life, and proceed in it with confidence.

It is true that, while busied only in considering the manners of other men, I found here, too, scarce any ground for

settled conviction, and remarked hardly less contradiction among them than in the opinions of the philosophers.

So that the greatest advantage I derived from the study consisted in this, that, observing many things which,

however extravagant and ridiculous to our apprehension, are yet by common consent received and approved by

other great nations, I learned to entertain too decided a belief in regard to nothing of the truth of which I had been

persuaded merely by example and custom; and thus I gradually extricated myself from many errors powerful

enough to darken our natural intelligence, and incapacitate us in great measure from listening to reason. But

after I had been occupied several years in thus studying the book of the world, and in essaying to gather some

experience, I at length resolved to make myself an object of study, and to employ all the powers of my mind in

choosing the paths I ought to follow, an undertaking which was accompanied with greater success than it would

have been had I never quitted my country or my books.

Chapter 2

I was then in Germany, attracted thither by the wars in that country, which have not yet been brought to a

termination; and as I was returning to the army from the coronation of the emperor, the setting in of winter

arrested me in a locality where, as I found no society to interest me, and was besides fortunately undisturbed by

any cares or passions, I remained the whole day in seclusion, with full opportunity to occupy my attention with my

own thoughts. Of these one of the very first that occurred to me was, that there is seldom so much perfection in

works composed of many separate parts, upon which different hands had been employed, as in those

completed by a single master. Thus it is observable that the buildings which a single architect has planned and

executed, are generally more elegant and commodious than those which several have attempted to improve, by

making old walls serve for purposes for which they were not originally built. Thus also, those ancient cities which,

from being at first only villages, have become, in course of time, large towns, are usually but ill laid out compared

with the regularity constructed towns which a professional architect has freely planned on an open plain; so that

although the several buildings of the former may often equal or surpass in beauty those of the latter, yet when

one observes their indiscriminate juxtaposition, there a large one and here a small, and the consequent

crookedness and irregularity of the streets, one is disposed to allege that chance rather than any human will

guided by reason must have led to such an arrangement. And if we consider that nevertheless there have been

at all times certain officers whose duty it was to see that private buildings contributed to public ornament, the

difficulty of reaching high perfection with but the materials of others to operate on, will be readily acknowledged.

In the same way I fancied that those nations which, starting from a semi-barbarous state and advancing to

civilization by slow degrees, have had their laws successively determined, and, as it were, forced upon them

simply by experience of the hurtfulness of particular crimes and disputes, would by this process come to be

possessed of less perfect institutions than those which, from the commencement of their association as

communities, have followed the appointments of some wise legislator. It is thus quite certain that the constitution

of the true religion, the ordinances of which are derived from God, must be incomparably superior to that of

every other. And, to speak of human affairs, I believe that the pre-eminence of Sparta was due not to the

goodness of each of its laws in particular, for many of these were very strange, and even opposed to good

morals, but to the circumstance that, originated by a single individual, they all tended to a single end. In the same

way I thought that the sciences contained in books (such of them at least as are made up of probable

reasonings, without demonstrations), composed as they are of the opinions of many different individuals

massed together, are farther removed from truth than the simple inferences which a man of good sense using

his natural and unprejudiced judgment draws respecting the matters of his experience. And because we have all

to pass through a state of infancy to manhood, and have been of necessity, for a length of time, governed by our

desires and preceptors (whose dictates were frequently conflicting, while neither perhaps always counseled us

for the best), I farther concluded that it is almost impossible that our judgments can be so correct or solid as they

would have been, had our reason been mature from the moment of our birth, and had we always been guided by

it alone.

It is true, however, that it is not customary to pull down all the houses of a town with the single design of

rebuilding them differently, and thereby rendering the streets more handsome; but it often happens that a private

individual takes down his own with the view of erecting it anew, and that people are even sometimes

constrained to this when their houses are in danger of falling from age, or when the foundations are insecure.

With this before me by way of example, I was persuaded that it would indeed be preposterous for a private

individual to think of reforming a state by fundamentally changing it throughout, and overturning it in order to set it

up amended; and the same I thought was true of any similar project for reforming the body of the sciences, or

the order of teaching them established in the schools: but as for the opinions which up to that time I had

embraced, I thought that I could not do better than resolve at once to sweep them wholly away, that I might

afterwards be in a position to admit either others more correct, or even perhaps the same when they had

undergone the scrutiny of reason. I firmly believed that in this way I should much better succeed in the conduct of

my life, than if I built only upon old foundations, and leaned upon principles which, in my youth, I had taken upon

trust. For although I recognized various difficulties in this undertaking, these were not, however, without remedy,

nor once to be compared with such as attend the slightest reformation in public affairs. Large bodies, if once

overthrown, are with great difficulty set up again, or even kept erect when once seriously shaken, and the fall of

such is always disastrous. Then if there are any imperfections in the constitutions of states (and that many such

exist the diversity of constitutions is alone sufficient to assure us), custom has without doubt materially smoothed

their inconveniences, and has even managed to steer altogether clear of, or insensibly corrected a number

which sagacity could not have provided against with equal effect; and, in fine, the defects are almost always

more tolerable than the change necessary for their removal; in the same manner that highways which wind

among mountains, by being much frequented, become gradually so smooth and commodious, that it is much

better to follow them than to seek a straighter path by climbing over the tops of rocks and descending to the

bottoms of precipices.

Hence it is that I cannot in any degree approve of those restless and busy meddlers who, called neither by birth

nor fortune to take part in the management of public affairs, are yet always projecting reforms; and if I thought

that this tract contained aught which might justify the suspicion that I was a victim of such folly, I would by no

means permit its publication. I have never contemplated anything higher than the reformation of my own

opinions, and basing them on a foundation wholly my own. And although my own satisfaction with my work has

led me to present here a draft of it, I do not by any means therefore recommend to every one else to make a

similar attempt. Those whom God has endowed with a larger measure of genius will entertain, perhaps, designs

still more exalted; but for the many I am much afraid lest even the present undertaking be more than they can

safely venture to imitate. The single design to strip one's self of all past beliefs is one that ought not to be taken

by every one. The majority of men is composed of two classes, for neither of which would this be at all a befitting

resolution: in the first place, of those who with more than a due confidence in their own powers, are precipitate in

their judgments and want the patience requisite for orderly and circumspect thinking; whence it happens, that if

men of this class once take the liberty to doubt of their accustomed opinions, and quit the beaten highway, they

will never be able to thread the byway that would lead them by a shorter course, and will lose themselves and

continue to wander for life; in the second place, of those who, possessed of sufficient sense or modesty to

determine that there are others who excel them in the power of discriminating between truth and error, and by

whom they may be instructed, ought rather to content themselves with the opinions of such than trust for more

correct to their own reason.

For my own part, I should doubtless have belonged to the latter class, had I received instruction from but one

master, or had I never known the diversities of opinion that from time immemorial have prevailed among men of

the greatest learning. But I had become aware, even so early as during my college life, that no opinion, however

absurd and incredible, can be imagined, which has not been maintained by some on of the philosophers; and

afterwards in the course of my travels I remarked that all those whose opinions are decidedly repugnant to ours

are not in that account barbarians and savages, but on the contrary that many of these nations make an equally

good, if not better, use of their reason than we do. I took into account also the very different character which a

person brought up from infancy in France or Germany exhibits, from that which, with the same mind originally,

this individual would have possessed had he lived always among the Chinese or with savages, and the

circumstance that in dress itself the fashion which pleased us ten years ago, and which may again, perhaps, be

received into favor before ten years have gone, appears to us at this moment extravagant and ridiculous. I was

thus led to infer that the ground of our opinions is far more custom and example than any certain knowledge.

And, finally, although such be the ground of our opinions, I remarked that a plurality of suffrages is no guarantee

of truth where it is at all of difficult discovery, as in such cases it is much more likely that it will be found by one

than by many. I could, however, select from the crowd no one whose opinions seemed worthy of preference, and

thus I found myself constrained, as it were, to use my own reason in the conduct of my life.

But like one walking alone and in the dark, I resolved to proceed so slowly and with such circumspection, that if I

did not advance far, I would at least guard against falling. I did not even choose to dismiss summarily any of the

opinions that had crept into my belief without having been introduced by reason, but first of all took sufficient

time carefully to satisfy myself of the general nature of the task I was setting myself, and ascertain the true

method by which to arrive at the knowledge of whatever lay within the compass of my powers.

Among the branches of philosophy, I had, at an earlier period, given some attention to logic, and among those

of the mathematics to geometrical analysis and algebra, -- three arts or sciences which ought, as I conceived, to

contribute something to my design. But, on examination, I found that, as for logic, its syllogisms and the majority

of its other precepts are of avail- rather in the communication of what we already know, or even as the art of

Lully, in speaking without judgment of things of which we are ignorant, than in the investigation of the unknown;

and although this science contains indeed a number of correct and very excellent precepts, there are,

nevertheless, so many others, and these either injurious or superfluous, mingled with the former, that it is almost

quite as difficult to effect a severance of the true from the false as it is to extract a Diana or a Minerva from a

rough block of marble. Then as to the analysis of the ancients and the algebra of the moderns, besides that they

embrace only matters highly abstract, and, to appearance, of no use, the former is so exclusively restricted to

the consideration of figures, that it can exercise the understanding only on condition of greatly fatiguing the

imagination; and, in the latter, there is so complete a subjection to certain rules and formulas, that there results

an art full of confusion and obscurity calculated to embarrass, instead of a science fitted to cultivate the mind. By

these considerations I was induced to seek some other method which would comprise the advantages of the

three and be exempt from their defects. And as a multitude of laws often only hampers justice, so that a state is

best governed when, with few laws, these are rigidly administered; in like manner, instead of the great number

of precepts of which logic is composed, I believed that the four following would prove perfectly sufficient for me,

provided I took the firm and unwavering resolution never in a single instance to fail in observing them.

The first was never to accept anything for true which I did not clearly know to be such; that is to say, carefully to avoid precipitancy and prejudice, and to comprise nothing more in my judgement than what was presented to my mind so clearly and distinctly as to exclude all ground of doubt.

The second, to divide each of the difficulties under examination into as many parts as possible, and as might be

necessary for its adequate solution.

The third, to conduct my thoughts in such order that, by commencing with objects the simplest and easiest to

know, I might ascend by little and little, and, as it were, step by step, to the knowledge of the more complex;

assigning in thought a certain order even to those objects which in their own nature do not stand in a relation of

antecedence and sequence.

And the last, in every case to make enumerations so complete, and reviews so general, that I might be assured

that nothing was omitted.

The long chains of simple and easy reasonings by means of which geometers are accustomed to reach the

conclusions of their most difficult demonstrations, had led me to imagine that all things, to the knowledge of

which man is competent, are mutually connected in the same way, and that there is nothing so far removed from

us as to be beyond our reach, or so hidden that we cannot discover it, provided only we abstain from accepting

the false for the true, and always preserve in our thoughts the order necessary for the deduction of one truth from

another. And I had little difficulty in determining the objects with which it was necessary to commence, for I was

already persuaded that it must be with the simplest and easiest to know, and, considering that of all those who

have hitherto sought truth in the sciences, the mathematicians alone have been able to find any demonstrations,

that is, any certain and evident reasons, I did not doubt but that such must have been the rule of their

investigations. I resolved to commence, therefore, with the examination of the simplest objects, not anticipating,

however, from this any other advantage than that to be found in accustoming my mind to the love and

nourishment of truth, and to a distaste for all such reasonings as were unsound. But I had no intention on that

account of attempting to master all the particular sciences commonly denominated mathematics: but observing

that, however different their objects, they all agree in considering only the various relations or proportions

subsisting among those objects, I thought it best for my purpose to consider these proportions in the most

general form possible, without referring them to any objects in particular, except such as would most facilitate

the knowledge of them, and without by any means restricting them to these, that afterwards I might thus be the

better able to apply them to every other class of objects to which they are legitimately applicable. Perceiving

further, that in order to understand these relations I should sometimes have to consider them one by one and

sometimes only to bear them in mind, or embrace them in the aggregate, I thought that, in order the better to

consider them individually, I should view them as subsisting between straight lines, than which I could find no

objects more simple, or capable of being more distinctly represented to my imagination and senses; and on the

other hand, that in order to retain them in the memory or embrace an aggregate of many, I should express them

by certain characters the briefest possible. In this way I believed that I could borrow all that was best both in

geometrical analysis and in algebra, and correct all the defects of the one by help of the other.

And, in point of fact, the accurate observance of these few precepts gave me, I take the liberty of saying, such

ease in unraveling all the questions embraced in these two sciences, that in the two or three months I devoted to

their examination, not only did I reach solutions of questions I had formerly deemed exceedingly difficult but even

as regards questions of the solution of which I continued ignorant, I was enabled, as it appeared to me, to

determine the means whereby, and the extent to which a solution was possible; results attributable to the

circumstance that I commenced with the simplest and most general truths, and that thus each truth discovered

was a rule available in the discovery of subsequent ones Nor in this perhaps shall I appear too vain, if it be

considered that, as the truth on any particular point is one whoever apprehends the truth, knows all that on that

point can be known. The child, for example, who has been instructed in the elements of arithmetic, and has

made a particular addition, according to rule, may be assured that he has found, with respect to the sum of the

numbers before him, and that in this instance is within the reach of human genius. Now, in conclusion, the

method which teaches adherence to the true order, and an exact enumeration of all the conditions of the thing

.sought includes all that gives certitude to the rules of arithmetic.

But the chief ground of my satisfaction with thus method, was the assurance I had of thereby exercising my

reason in all matters, if not with absolute perfection, at least with the greatest attainable by me: besides, I was

conscious that by its use my mind was becoming gradually habituated to clearer and more distinct conceptions

of its objects; and I hoped also, from not having restricted this method to any particular matter, to apply it to the

difficulties of the other sciences, with not less success than to those of algebra. I should not, however, on this

account have ventured at once on the examination of all the difficulties of the sciences which presented

themselves to me, for this would have been contrary to the order prescribed in the method, but observing that

the knowledge of such is dependent on principles borrowed from philosophy, in which I found nothing certain, I

thought it necessary first of all to endeavor to establish its principles. .And because I observed, besides, that an

inquiry of this kind was of all others of the greatest moment, and one in which precipitancy and anticipation in

judgment were most to be dreaded, I thought that I ought not to approach it till I had reached a more mature age

(being at that time but twenty-three), and had first of all employed much of my time in preparation for the work, as

well by eradicating from my mind all the erroneous opinions I had up to that moment accepted, as by amassing

variety of experience to afford materials for my reasonings, and by continually exercising myself in my chosen

method with a view to increased skill in its application.

Chapter 3

And finally, as it is not enough, before commencing to rebuild the house in which we live, that it be pulled down,

and materials and builders provided, or that we engage in the work ourselves, according to a plan which we

have beforehand carefully drawn out, but as it is likewise necessary that we be furnished with some other house

in which we may live commodiously during the operations, so that I might not remain irresolute in my actions,

while my reason compelled me to suspend my judgment, and that I might not be prevented from living

thenceforward in the greatest possible felicity, I formed a provisory code of morals, composed of three or four

maxims, with which I am desirous to make you acquainted.

The first was to obey the laws and customs of my country, adhering firmly to the faith in which, by the grace of

God, I had been educated from my childhood and regulating my conduct in every other matter according to the

most moderate opinions, and the farthest removed from extremes, which should happen to be adopted in

practice with general consent of the most judicious of those among whom I might be living. For as I had from that

time begun to hold my own opinions for nought because I wished to subject them all to examination, I was

convinced that I could not do better than follow in the meantime the opinions of the most judicious; and although

there are some perhaps among the Persians and Chinese as judicious as among ourselves, expediency

seemed to dictate that I should regulate my practice conformably to the opinions of those with whom I should

have to live; and it appeared to me that, in order to ascertain the real opinions of such, I ought rather to take

cognizance of what they practised than of what they said, not only because, in the corruption of our manners,

there are few disposed to speak exactly as they believe, but also because very many are not aware of what it is

that they really believe; for, as the act of mind by which a thing is believed is different from that by which we know

that we believe it, the one act is often found without the other. Also, amid many opinions held in equal repute, I

chose always the most moderate, as much for the reason that these are always the most convenient for

practice, and probably the best (for all excess is generally vicious), as that, in the event of my falling into error, I

might be at less distance from the truth than if, having chosen one of the extremes, it should turn out to be the

other which I ought to have adopted. And I placed in the class of extremes especially all promises by which

somewhat of our freedom is abridged; not that I disapproved of the laws which, to provide against the instability

of men of feeble resolution, when what is sought to be accomplished is some good, permit engagements by

vows and contracts binding the parties to persevere in it, or even, for the security of commerce, sanction similar

engagements where the purpose sought to be realized is indifferent: but because I did not find anything on earth

which was wholly superior to change, and because, for myself in particular, I hoped gradually to perfect my

judgments, and not to suffer them to deteriorate, I would have deemed it a grave sin against good sense, if, for

the reason that I approved of something at a particular time, I therefore bound myself to hold it for good at a

subsequent time, when perhaps it had ceased to be so, or I had ceased to esteem it such.

My second maxim was to be as firm and resolute in my actions as I was able, and not to adhere less steadfastly

to the most doubtful opinions, when once adopted, than if they had been highly certain; imitating in this the

example of travelers who, when they have lost their way in a forest, ought not to wander from side to side, far

less remain in one place, but proceed constantly towards the same side in as straight a line as possible, without

changing their direction for slight reasons, although perhaps it might be chance alone which at first determined

the selection; for in this way, if they do not exactly reach the point they desire, they will come at least in the end to

some place that will probably be preferable to the middle of a forest. In the same way, since in action it

frequently happens that no delay is permissible, it is very certain that, when it is not in our power to determine

what is true, we ought to act according to what is most probable; and even although we should not remark a

greater probability in one opinion than in another, we ought notwithstanding to choose one or the other, and

afterwards consider it, in so far as it relates to practice, as no longer dubious, but manifestly true and certain,

since the reason by which our choice has been determined is itself possessed of these qualities. This principle

was sufficient thenceforward to rid me of all those repentings and pangs of remorse that usually disturb the

consciences of such feeble and uncertain minds as, destitute of any clear and determinate principle of choice,

allow themselves one day to adopt a course of action as the best, which they abandon the next, as the opposite.

My third maxim was to endeavor always to conquer myself rather than fortune, and change my desires rather

than the order of the world, and in general, accustom myself to the persuasion that, except our own thoughts,

there is nothing absolutely in our power; so that when we have done our best in things external to us, all wherein

we fail of success is to be held, as regards us, absolutely impossible: and this single principle seemed to me

sufficient to prevent me from desiring for the future anything which I could not obtain, and thus render me

contented; for since our will naturally seeks those objects alone which the understanding represents as in some

way possible of attainment, it is plain, that if we consider all external goods as equally beyond our power, we

shall no more regret the absence of such goods as seem due to our birth, when deprived of them without any

fault of ours, than our not possessing the kingdoms of China or Mexico, and thus making, so to speak, a virtue of

necessity, we shall no more desire health in disease, or freedom in imprisonment, than we now do bodies

incorruptible as diamonds, or the wings of birds to fly with. But I confess there is need of prolonged discipline

and frequently repeated meditation to accustom the mind to view all objects in this light; and I believe that in this

chiefly consisted the secret of the power of such philosophers as in former times were enabled to rise superior

to the influence of fortune, and, amid suffering and poverty, enjoy a happiness which their gods might have

envied. For, occupied incessantly with the consideration of the limits prescribed to their power by nature, they

became so entirely convinced that nothing was at their disposal except their own thoughts, that this conviction

was of itself sufficient to prevent their entertaining any desire of other objects; and over their thoughts they

acquired a sway so absolute, that they had some ground on this account for esteeming themselves more rich

and more powerful, more free and more happy, than other men who, whatever be the favors heaped on them by

nature and fortune, if destitute of this philosophy, can never command the realization of all their desires.

In fine, to conclude this code of morals, I thought of reviewing the different occupations of men in this life, with the

view of making choice of the best. And, without wishing to offer any remarks on the employments of others, I

may state that it was my conviction that I could not do better than continue in that in which I was engaged, viz., in

devoting my whole life to the culture of my reason, and in making the greatest progress I was able in the

knowledge of truth, on the principles of the method which I had prescribed to myself. This method, from the time I

had begun to apply it, had been to me the source of satisfaction so intense as to lead me to, believe that more

perfect or more innocent could not be enjoyed in this life; and as by its means I daily discovered truths that

appeared to me of some importance, and of which other men were generally ignorant, the gratification thence

arising so occupied my mind that I was wholly indifferent to every other object. Besides, the three preceding

maxims were founded singly on the design of continuing the work of self- instruction. For since God has

endowed each of us with some light of reason by which to distinguish truth from error, I could not have believed

that I ought for a single moment to rest satisfied with the opinions of another, unless I had resolved to exercise

my own judgment in examining these whenever I should be duly qualified for the task. Nor could I have

proceeded on such opinions without scruple, had I supposed that I should thereby forfeit any advantage for

attaining still more accurate, should such exist. And, in fine, I could not have restrained my desires, nor remained

satisfied had I not followed a path in which I thought myself certain of attaining all the knowledge to the

acquisition of which I was competent, as well as the largest amount of what is truly good which I could ever hope

to secure Inasmuch as we neither seek nor shun any object except in so far as our understanding represents it

as good or bad, all that is necessary to right action is right judgment, and to the best action the most correct

judgment, that is, to the acquisition of all the virtues with all else that is truly valuable and within our reach; and

the assurance of such an acquisition cannot fail to render us contented.

Having thus provided myself with these maxims, and having placed them in reserve along with the truths of faith,

which have ever occupied the first place in my belief, I came to the conclusion that I might with freedom set

about ridding myself of what remained of my opinions. And, inasmuch as I hoped to be better able successfully

to accomplish this work by holding intercourse with mankind, than by remaining longer shut up in the retirement

where these thoughts had occurred to me, I betook me again to traveling before the winter was well ended. And,

during the nine subsequent years, I did nothing but roam from one place to another, desirous of being a

spectator rather than an actor in the plays exhibited on the theater of the world; and, as I made it my business in

each matter to reflect particularly upon what might fairly be doubted and prove a source of error, I gradually

rooted out from my mind all the errors which had hitherto crept into it. Not that in this I imitated the sceptics who

doubt only that they may doubt, and seek nothing beyond uncertainty itself; for, on the contrary, my design was

singly to find ground of assurance, and cast aside the loose earth and sand, that I might reach the rock or the

clay. In this, as appears to me, I was successful enough; for, since I endeavored to discover the falsehood or

incertitude of the propositions I examined, not by feeble conjectures, but by clear and certain reasonings, I met

with nothing so doubtful as not to yield some conclusion of adequate certainty, although this were merely the

inference, that the matter in question contained nothing certain. And, just as in pulling down an old house, we

usually reserve the ruins to contribute towards the erection, so, in destroying such of my opinions as I judged to

be Ill-founded, I made a variety of observations and acquired an amount of experience of which I availed myself

in the establishment of more certain. And further, I continued to exercise myself in the method I had prescribed;

for, besides taking care in general to conduct all my thoughts according to its rules, I reserved some hours from

time to time which I expressly devoted to the employment of the method in the solution of mathematical

difficulties, or even in the solution likewise of some questions belonging to other sciences, but which, by my

having detached them from such principles of these sciences as were of inadequate certainty, were rendered

almost mathematical: the truth of this will be manifest from the numerous examples contained in this volume.

And thus, without in appearance living otherwise than those who, with no other occupation than that of spending

their lives agreeably and innocently, study to sever pleasure from vice, and who, that they may enjoy their leisure

without ennui, have recourse to such pursuits as are honorable, I was nevertheless prosecuting my design, and

making greater progress in the knowledge of truth, than I might, perhaps, have made had I been engaged in the

perusal of books merely, or in holding converse with men of letters.

These nine years passed away, however, before I had come to any determinate judgment respecting the

difficulties which form matter of dispute among the learned, or had commenced to seek the principles of any

philosophy more certain than the vulgar. And the examples of many men of the highest genius, who had, in

former times, engaged in this inquiry, but, as appeared to me, without success, led me to imagine it to be a

work of so much difficulty, that I would not perhaps have ventured on it so soon had I not heard it currently

rumored that I had already completed the inquiry. I know not what were the grounds of this opinion; and, if my

conversation contributed in any measure to its rise, this must have happened rather from my having confessed

my Ignorance with greater freedom than those are accustomed to do who have studied a little, and expounded

perhaps, the reasons that led me to doubt of many of those things that by others are esteemed certain, than

from my having boasted of any system of philosophy. But, as I am of a disposition that makes me unwilling to be

esteemed different from what I really am, I thought it necessary to endeavor by all means to render myself worthy

of the reputation accorded to me; and it is now exactly eight years since this desire constrained me to remove

from all those places where interruption from any of my acquaintances was possible, and betake myself to this

country, in which the long duration of the war has led to the establishment of such discipline, that the armies

maintained seem to be of use only in enabling the inhabitants to enjoy more securely the blessings of peace and

where, in the midst of a great crowd actively engaged in business, and more careful of their own affairs than

curious about those of others, I have been enabled to live without being deprived of any of the conveniences to

be had in the most populous cities, and yet as solitary and as retired as in the midst of the most remote deserts.

Chapter 4

I am in doubt as to the propriety of making my first meditations in the place above mentioned matter of

discourse; for these are so metaphysical, and so uncommon, as not, perhaps, to be acceptable to every one.

And yet, that it may be determined whether the foundations that I have laid are sufficiently secure, I find myself in

a measure constrained to advert to them. I had long before remarked that, in relation to practice, it is sometimes

necessary to adopt, as if above doubt, opinions which we discern to be highly uncertain, as has been already

said; but as I then desired to give my attention solely to the search after truth, I thought that a procedure exactly

the opposite was called for, and that I ought to reject as absolutely false all opinions in regard to which I could

suppose the least ground for doubt, in order to ascertain whether after that there remained aught in my belief

that was wholly indubitable. Accordingly, seeing that our senses sometimes deceive us, I was willing to suppose

that there existed nothing really such as they presented to us; and because some men err in reasoning, and fall

into paralogisms, even on the simplest matters of geometry, I, convinced that I was as open to error as any

other, rejected as false all the reasonings I had hitherto taken for demonstrations; and finally, when I considered

that the very same thoughts (presentations) which we experience when awake may also be experienced when

we are asleep, while there is at that time not one of them true, I supposed that all the objects (presentations) that

had ever entered into my mind when awake, had in them no more truth than the illusions of my dreams. But

immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary

that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am (COGITO

ERGO SUM), was so certain and of such evidence that no ground of doubt, however extravagant, could be

alleged by the sceptics capable of shaking it, I concluded that I might, without scruple, accept it as the first

principle of the philosophy of which I was in search

In the next place, I attentively examined what I was and as I observed that I could suppose that I had no body, and

that there was no world nor any place in which I might be; but that I could not therefore suppose that I was not;

and that, on the contrary, from the very circumstance that I thought to doubt of the truth of other things, it most

clearly and certainly followed that I was; while, on the other hand, if I had only ceased to think, although all the

other objects which I had ever imagined had been in reality existent, I would have had no reason to believe that I

existed; I thence concluded that I was a substance whose whole essence or nature consists only in thinking, and

which, that it may exist, has need of no place, nor is dependent on any material thing; so that " I," that is to say,

the mind by which I am what I am, is wholly distinct from the body, and is even more easily known than the latter,

and is such, that although the latter were not, it would still continue to be all that it is.

After this I inquired in general into what is essential I to the truth and certainty of a proposition; for since I had

discovered one which I knew to be true, I thought that I must likewise be able to discover the ground of this

certitude. And as I observed that in the words I think, therefore I am, there is nothing at all which gives me assurance of their truth beyond this, that I see very clearly that in order to think it is necessary to exist, I concluded that I might take, as a general rule, the principle, that all the things which we very clearly and distinctly conceive are true, only observing, however, that there is some difficulty in rightly determining the objects which

we distinctly conceive.

In the next place, from reflecting on the circumstance that I doubted, and that consequently my being was not

wholly perfect (for I clearly saw that it was a greater perfection to know than to doubt), I was led to inquire

whence I had learned to think of something more perfect than myself; and I clearly recognized that I must hold

this notion from some nature which in reality was more perfect. As for the thoughts of many other objects

external to me, as of the sky, the earth, light, heat, and a thousand more, I was less at a loss to know whence

these came; for since I remarked in them nothing which seemed to render them superior to myself, I could

believe that, if these were true, they were dependencies on my own nature, in so far as it possessed a certain

perfection, and, if they were false, that I held them from nothing, that is to say, that they were in me because of a

certain imperfection of my nature. But this could not be the case with-the idea of a nature more perfect than

myself; for to receive it from nothing was a thing manifestly impossible; and, because it is not less repugnant that

the more perfect should be an effect of, and dependence on the less perfect, than that something should

proceed from nothing, it was equally impossible that I could hold it from myself: accordingly, it but remained that

it had been placed in me by a nature which was in reality more perfect than mine, and which even possessed

within itself all the perfections of which I could form any idea; that is to say, in a single word, which was God. And

to this I added that, since I knew some perfections which I did not possess, I was not the only being in existence

(I will here, with your permission, freely use the terms of the schools); but, on the contrary, that there was of

necessity some other more perfect Being upon whom I was dependent, and from whom I had received all that I

possessed; for if I had existed alone, and independently of every other being, so as to have had from myself all

the perfection, however little, which I actually possessed, I should have been able, for the same reason, to have

had from myself the whole remainder of perfection, of the want of which I was conscious, and thus could of

myself have become infinite, eternal, immutable, omniscient, all-powerful, and, in fine, have possessed all the

perfections which I could recognize in God. For in order to know the nature of God (whose existence has been

established by the preceding reasonings), as far as my own nature permitted, I had only to consider in reference

to all the properties of which I found in my mind some idea, whether their possession was a mark of perfection;

and I was assured that no one which indicated any imperfection was in him, and that none of the rest was

awanting. Thus I perceived that doubt, inconstancy, sadness, and such like, could not be found in God, since I

myself would have been happy to be free from them. Besides, I had ideas of many sensible and corporeal

things; for although I might suppose that I was dreaming, and that all which I saw or imagined was false, I could

not, nevertheless, deny that the ideas were in reality in my thoughts. But, because I had already very clearly

recognized in myself that the intelligent nature is distinct from the corporeal, and as I observed that all

composition is an evidence of dependency, and that a state of dependency is manifestly a state of imperfection,

I therefore determined that it could not be a perfection in God to be compounded of these two natures and that

consequently he was not so compounded; but that if there were any bodies in the world, or even any

intelligences, or other natures that were not wholly perfect, their existence depended on his power in such a way

that they could not subsist without him for a single moment.

I was disposed straightway to search for other truths and when I had represented to myself the object of the

geometers, which I conceived to be a continuous body or a space indefinitely extended in length, breadth, and

height or depth, divisible into divers parts which admit of different figures and sizes, and of being moved or

transposed in all manner of ways (for all this the geometers suppose to be in the object they contemplate), I went

over some of their simplest demonstrations. And, in the first place, I observed, that the great certitude which by

common consent is accorded to these demonstrations, is founded solely upon this, that they are clearly

conceived in accordance with the rules I have already laid down In the next place, I perceived that there was

nothing at all in these demonstrations which could assure me of the existence of their object: thus, for example,

supposing a triangle to be given, I distinctly perceived that its three angles were necessarily equal to two right

angles, but I did not on that account perceive anything which could assure me that any triangle existed: while, on

the contrary, recurring to the examination of the idea of a Perfect Being, I found that the existence of the Being

was comprised in the idea in the same way that the equality of its three angles to two right angles is comprised

in the idea of a triangle, or as in the idea of a sphere, the equidistance of all points on its surface from the

center, or even still more clearly; and that consequently it is at least as certain that God, who is this Perfect

Being, is, or exists, as any demonstration of geometry can be.

But the reason which leads many to persuade them selves that there is a difficulty in knowing this truth, and even

also in knowing what their mind really is, is that they never raise their thoughts above sensible objects, and are

so accustomed to consider nothing except by way of imagination, which is a mode of thinking limited to material

objects, that all that is not imaginable seems to them not intelligible. The truth of this is sufficiently manifest from

the single circumstance, that the philosophers of the schools accept as a maxim that there is nothing in the

understanding which was not previously in the senses, in which however it is certain that the ideas of God and of

the soul have never been; and it appears to me that they who make use of their imagination to comprehend

these ideas do exactly the some thing as if, in order to hear sounds or smell odors, they strove to avail

themselves of their eyes; unless indeed that there is this difference, that the sense of sight does not afford us an

inferior assurance to those of smell or hearing; in place of which, neither our imagination nor our senses can

give us assurance of anything unless our understanding intervene.

Finally, if there be still persons who are not sufficiently persuaded of the existence of God and of the soul, by the

reasons I have adduced, I am desirous that they should know that all the other propositions, of the truth of which

they deem themselves perhaps more assured, as that we have a body, and that there exist stars and an earth,

and such like, are less certain; for, although we have a moral assurance of these things, which is so strong that

there is an appearance of extravagance in doubting of their existence, yet at the same time no one, unless his

intellect is impaired, can deny, when the question relates to a metaphysical certitude, that there is sufficient

reason to exclude entire assurance, in the observation that when asleep we can in the same way imagine

ourselves possessed of another body and that we see other stars and another earth, when there is nothing of

the kind. For how do we know that the thoughts which occur in dreaming are false rather than those other which

we experience when awake, since the former are often not less vivid and distinct than the latter? And though

men of the highest genius study this question as long as they please, I do not believe that they will be able to

give any reason which can be sufficient to remove this doubt, unless they presuppose the existence of God. For,

in the first place even the principle which I have already taken as a rule, viz., that all the things which we clearly

and distinctly conceive are true, is certain only because God is or exists and because he is a Perfect Being, and

because all that we possess is derived from him: whence it follows that our ideas or notions, which to the extent

of their clearness and distinctness are real, and proceed from God, must to that extent be true. Accordingly,

whereas we not infrequently have ideas or notions in which some falsity is contained, this can only be the case

with such as are to some extent confused and obscure, and in this proceed from nothing (participate of

negation), that is, exist in us thus confused because we are not wholly perfect. And it is evident that it is not less

repugnant that falsity or imperfection, in so far as it is imperfection, should proceed from God, than that truth or

perfection should proceed from nothing. But if we did not know that all which we possess of real and true

proceeds from a Perfect and Infinite Being, however clear and distinct our ideas might be, we should have no

ground on that account for the assurance that they possessed the perfection of being true.

But after the knowledge of God and of the soul has rendered us certain of this rule, we can easily understand

that the truth of the thoughts we experience when awake, ought not in the slightest degree to be called in

question on account of the illusions of our dreams. For if it happened that an individual, even when asleep, had

some very distinct idea, as, for example, if a geometer should discover some new demonstration, the

circumstance of his being asleep would not militate against its truth; and as for the most ordinary error of our

dreams, which consists in their representing to us various objects in the same way as our external senses, this

is not prejudicial, since it leads us very properly to suspect the truth of the ideas of sense; for we are not

infrequently deceived in the same manner when awake; as when persons in the jaundice see all objects yellow,

or when the stars or bodies at a great distance appear to us much smaller than they are. For, in fine, whether

awake or asleep, we ought never to allow ourselves to be persuaded of the truth of anything unless on the

evidence of our reason. And it must be noted that I say of our reason, and not of our imagination or of our

senses: thus, for example, although we very clearly see the sun, we ought not therefore to determine that it is

only of the size which our sense of sight presents; and we may very distinctly imagine the head of a lion joined to

the body of a goat, without being therefore shut up to the conclusion that a chimaera exists; for it is not a dictate

of reason that what we thus see or imagine is in reality existent; but it plainly tells us that all our ideas or notions

contain in them some truth; for otherwise it could not be that God, who is wholly perfect and veracious, should

have placed them in us. And because our reasonings are never so clear or so complete during sleep as when

we are awake, although sometimes the acts of our imagination are then as lively and distinct, if not more so than

in our waking moments, reason further dictates that, since all our thoughts cannot be true because of our partial

imperfection, those possessing truth must infallibly be found in the experience of our waking moments rather

than in that of our dreams.

Chapter 5

I would here willingly have proceeded to exhibit the whole chain of truths which I deduced from these primary but

as with a view to this it would have been necessary now to treat of many questions in dispute among the learned,

with whom I do not wish to be embroiled, I believe that it will be better for me to refrain from this exposition, and

only mention in general what these truths are, that the more judicious may be able to determine whether a more

special account of them would conduce to the public advantage. I have ever remained firm in my original

resolution to suppose no other principle than that of which I have recently availed myself in demonstrating the

existence of God and of the soul, and to accept as true nothing that did not appear to me more clear and certain

than the demonstrations of the geometers had formerly appeared; and yet I venture to state that not only have I

found means to satisfy myself in a short time on all the principal difficulties which are usually treated of in

philosophy, but I have also observed certain laws established in nature by God in such a manner, and of which

he has impressed on our minds such notions, that after we have reflected sufficiently upon these, we cannot

doubt that they are accurately observed in all that exists or takes place in the world and farther, by considering

the concatenation of these laws, it appears to me that I have discovered many truths more useful and more

important than all I had before learned, or even had expected to learn.

But because I have essayed to expound the chief of these discoveries in a treatise which certain considerations

prevent me from publishing, I cannot make the results known more conveniently than by here giving a summary

of the contents of this treatise. It was my design to comprise in it all that, before I set myself to write it, I thought I

knew of the nature of material objects. But like the painters who, finding themselves unable to represent equally

well on a plain surface all the different faces of a solid body, select one of the chief, on which alone they make

the light fall, and throwing the rest into the shade, allow them to appear only in so far as they can be seen while

looking at the principal one; so, fearing lest I should not be able to compense in my discourse all that was in my

mind, I resolved to expound singly, though at considerable length, my opinions regarding light; then to take the

opportunity of adding something on the sun and the fixed stars, since light almost wholly proceeds from them; on

the heavens since they transmit it; on the planets, comets, and earth, since they reflect it; and particularly on all

the bodies that are upon the earth, since they are either colored, or transparent, or luminous; and finally on man,

since he is the spectator of these objects. Further, to enable me to cast this variety of subjects somewhat into

the shade, and to express my judgment regarding them with greater freedom, without being necessitated to

adopt or refute the opinions of the learned, I resolved to leave all the people here to their disputes, and to speak

only of what would happen in a new world, if God were now to create somewhere in the imaginary spaces

matter sufficient to compose one, and were to agitate variously and confusedly the different parts of this matter,

so that there resulted a chaos as disordered as the poets ever feigned, and after that did nothing more than lend

his ordinary concurrence to nature, and allow her to act in accordance with the laws which he had established.

On this supposition, I, in the first place, described this matter, and essayed to represent it in such a manner that

to my mind there can be nothing clearer and more intelligible, except what has been recently said regarding

God and the soul; for I even expressly supposed that it possessed none of those forms or qualities which are so

debated in the schools, nor in general anything the knowledge of which is not so natural to our minds that no one

can so much as imagine himself ignorant of it. Besides, I have pointed out what are the laws of nature; and, with

no other principle upon which to found my reasonings except the infinite perfection of God, I endeavored to

demonstrate all those about which there could be any room for doubt, and to prove that they are such, that even

if God had created more worlds, there could have been none in which these laws were not observed. Thereafter,

I showed how the greatest part of the matter of this chaos must, in accordance with these laws, dispose and

arrange itself in such a way as to present the appearance of heavens; how in the meantime some of its parts

must compose an earth and some planets and comets, and others a sun and fixed stars. And, making a

digression at this stage on the subject of light, I expounded at considerable length what the nature of that light

must be which is found in the sun and the stars, and how thence in an instant of time it traverses the immense

spaces of the heavens, and how from the planets and comets it is reflected towards the earth. To this I likewise

added much respecting the substance, the situation, the motions, and all the different qualities of these heavens

and stars; so that I thought I had said enough respecting them to show that there is nothing observable in the

heavens or stars of our system that must not, or at least may not appear precisely alike in those of the system

which I described. I came next to speak of the earth in particular, and to show how, even though I had expressly

supposed that God had given no weight to the matter of which it is composed, this should not prevent all its

parts from tending exactly to its center; how with water and air on its surface, the disposition of the heavens and

heavenly bodies, more especially of the moon, must cause a flow and ebb, like in all its circumstances to that

observed in our seas, as also a certain current both of water and air from east to west, such as is likewise

observed between the tropics; how the mountains, seas, fountains, and rivers might naturally be formed in it, and

the metals produced in the mines, and the plants grow in the fields and in general, how all the bodies which are

commonly denominated mixed or composite might be generated and, among other things in the discoveries

alluded to inasmuch as besides the stars, I knew nothing except fire which produces light, I spared no pains to

set forth all that pertains to its nature, -- the manner of its production and support, and to explain how heat is

sometimes found without light, and light without heat; to show how it can induce various colors upon different

bodies and other diverse qualities; how it reduces some to a liquid state and hardens others; how it can

consume almost all bodies, or convert them into ashes and smoke; and finally, how from these ashes, by the

mere intensity of its action, it forms glass: for as this transmutation of ashes into glass appeared to me as

wonderful as any other in nature, I took a special pleasure in describing it. I was not, however, disposed, from

these circumstances, to conclude that this world had been created in the manner I described; for it is much more

likely that God made it at the first such as it was to be. But this is certain, and an opinion commonly received

among theologians, that the action by which he now sustains it is the same with that by which he originally

created it; so that even although he had from the beginning given it no other form than that of chaos, provided

only he had established certain laws of nature, and had lent it his concurrence to enable it to act as it is wont to

do, it may be believed, without discredit to the miracle of creation, that, in this way alone, things purely material

might, in course of time, have become such as we observe them at present; and their nature is much more

easily conceived when they are beheld coming in this manner gradually into existence, than when they are only

considered as produced at once in a finished and perfect state.

From the description of inanimate bodies and plants, I passed to animals, and particularly to man. But since I

had not as yet sufficient knowledge to enable me to treat of these in the same manner as of the rest, that is to

say, by deducing effects from their causes, and by showing from what elements and in what manner nature must

produce them, I remained satisfied with the supposition that God formed the body of man wholly like to one of

ours, as well in the external shape of the members as in the internal conformation of the organs, of the same

matter with that I had described, and at first placed in it no rational soul, nor any other principle, in room of the

vegetative or sensitive soul, beyond kindling in the heart one of those fires without light, such as I had already

described, and which I thought was not different from the heat in hay that has been heaped together before it is

dry, or that which causes fermentation in new wines before they are run clear of the fruit. For, when I examined

the kind of functions which might, as consequences of this supposition, exist in this body, I found precisely all

those which may exist in us independently of all power of thinking, and consequently without being in any

measure owing to the soul; in other words, to that part of us which is distinct from the body, and of which it has

been said above that the nature distinctively consists in thinking, functions in which the animals void of reason

may be said wholly to resemble us; but among which I could not discover any of those that, as dependent on

thought alone, belong to us as men, while, on the other hand, I did afterwards discover these as soon as I

supposed God to have created a rational soul, and to have annexed it to this body in a particular manner which I

described.

But, in order to show how I there handled this matter, I mean here to give the explication of the motion of the

heart and arteries, which, as the first and most general motion observed in animals, will afford the means of

readily determining what should be thought of all the rest. And that there may be less difficulty in understanding

what I am about to say on this subject, I advise those who are not versed in anatomy, before they commence the

perusal of these observations, to take the trouble of getting dissected in their presence the heart of some large

animal possessed of lungs (for this is throughout sufficiently like the human), and to have shown to them its two

ventricles or cavities: in the first place, that in the right side, with which correspond two very ample tubes, viz., the

hollow vein (vena cava), which is the principal receptacle of the blood, and the trunk of the tree, as it were, of

which all the other veins in the body are branches; and the arterial vein (vena arteriosa), inappropriately so

denominated, since it is in truth only an artery, which, taking its rise in the heart, is divided, after passing out

from it, into many branches which presently disperse themselves all over the lungs; in the second place, the

cavity in the left side, with which correspond in the same manner two canals in size equal to or larger than the

preceding, viz., the venous artery (arteriavenosa), likewise inappropriately thus designated, because it is simply

a vein which comes from the lungs, where it is divided into many branches, interlaced with those of the arterial

vein, and those of the tube called the windpipe, through which the air we breathe enters; and the great artery

which, issuing from the heart, sends its branches all over the body. I should wish also that such persons were

carefully shown the eleven pellicles which, like so many small valves, open and shut the four orifices that are in

these two cavities, viz., three at the entrance of the hollow veins where they are disposed in such a manner as by

no means to prevent the blood which it contains from flowing into the right ventricle of the heart, and yet exactly

to prevent its flowing out; three at the entrance to the arterial vein, which, arranged in a manner exactly the

opposite of the former, readily permit the blood contained in this cavity to pass into the lungs, but hinder that

contained in the lungs from returning to this cavity; and, in like manner, two others at the mouth of the venous

artery, which allow the blood from the lungs to flow into the left cavity of the heart, but preclude its return; and

three at the mouth of the great artery, which suffer the blood to flow from the heart, but prevent its reflux. Nor do

we need to seek any other reason for the number of these pellicles beyond this that the orifice of the venous

artery being of an oval shape from the nature of its situation, can be adequately closed with two, whereas the

others being round are more conveniently closed with three. Besides, I wish such persons to observe that the

grand artery and the arterial vein are of much harder and firmer texture than the venous artery and the hollow

vein; and that the two last expand before entering the heart, and there form, as it were, two pouches

denominated the auricles of the heart, which are composed of a substance similar to that of the heart itself; and

that there is always more warmth in the heart than in any other part of the body- and finally, that this heat is

capable of causing any drop of blood that passes into the cavities rapidly to expand and dilate, just as all liquors

do when allowed to fall drop by drop into a highly heated vessel.

For, after these things, it is not necessary for me to say anything more with a view to explain the motion of the

heart, except that when its cavities are not full of blood, into these the blood of necessity flows, - - from the hollow

vein into the right, and from the venous artery into the left; because these two vessels are always full of blood,

and their orifices, which are turned towards the heart, cannot then be closed. But as soon as two drops of blood

have thus passed, one into each of the cavities, these drops which cannot but be very large, because the

orifices through which they pass are wide, and the vessels from which they come full of blood, are immediately

rarefied, and dilated by the heat they meet with. In this way they cause the whole heart to expand, and at the

same time press home and shut the five small valves that are at the entrances of the two vessels from which they

flow, and thus prevent any more blood from coming down into the heart, and becoming more and more rarefied,

they push open the six small valves that are in the orifices of the other two vessels, through which they pass out,

causing in this way all the branches of the arterial vein and of the grand artery to expand almost simultaneously

with the heart which immediately thereafter begins to contract, as do also the arteries, because the blood that

has entered them has cooled, and the six small valves close, and the five of the hollow vein and of the venous

artery open anew and allow a passage to other two drops of blood, which cause the heart and the arteries again

to expand as before. And, because the blood which thus enters into the heart passes through these two

pouches called auricles, it thence happens that their motion is the contrary of that of the heart, and that when it

expands they contract. But lest those who are ignorant of the force of mathematical demonstrations and who are

not accustomed to distinguish true reasons from mere verisimilitudes, should venture. without examination, to

deny what has been said, I wish it to be considered that the motion which I have now explained follows as

necessarily from the very arrangement of the parts, which may be observed in the heart by the eye alone, and

from the heat which may be felt with the fingers, and from the nature of the blood as learned from experience, as

does the motion of a clock from the power, the situation, and shape of its counterweights and wheels.

But if it be asked how it happens that the blood in the veins, flowing in this way continually into the heart, is not

exhausted, and why the arteries do not become too full, since all the blood which passes through the heart flows

into them, I need only mention in reply what has been written by a physician 1 of England, who has the honor of

having broken the ice on this subject, and of having been the first to teach that there are many small passages at

the extremities of the arteries, through which the blood received by them from the heart passes into the small

branches of the veins, whence it again returns to the heart; so that its course amounts precisely to a perpetual

circulation. Of this we have abundant proof in the ordinary experience of surgeons, who, by binding the arm with

a tie of moderate straitness above the part where they open the vein, cause the blood to flow more copiously

than it would have done without any ligature; whereas quite the contrary would happen were they to bind it below;

that is, between the hand and the opening, or were to make the ligature above the opening very tight. For it is

manifest that the tie, moderately straightened, while adequate to hinder the blood already in the arm from

returning towards the heart by the veins, cannot on that account prevent new blood from coming forward through

the arteries, because these are situated below the veins, and their coverings, from their greater consistency, are

more difficult to compress; and also that the blood which comes from the heart tends to pass through them to the

hand with greater force than it does to return from the hand to the heart through the veins. And since the latter

current escapes from the arm by the opening made in one of the veins, there must of necessity be certain

passages below the ligature, that is, towards the extremities of the arm through which it can come thither from

the arteries. This physician likewise abundantly establishes what he has advanced respecting the motion of the

blood, from the existence of certain pellicles, so disposed in various places along the course of the veins, in the

manner of small valves, as not to permit the blood to pass from the middle of the body towards the extremities,

but only to return from the extremities to the heart; and farther, from experience which shows that all the blood

which is in the body may flow out of it in a very short time through a single artery that has been cut, even although

this had been closely tied in the immediate neighborhood of the heart and cut between the heart and the

ligature, so as to prevent the supposition that the blood flowing out of it could come from any other quarter than

the heart.

But there are many other circumstances which evince that what I have alleged is the true cause of the motion of

the blood: thus, in the first place, the difference that is observed between the blood which flows from the veins,

and that from the arteries, can only arise from this, that being rarefied, and, as it were, distilled by passing

through the heart, it is thinner, and more vivid, and warmer immediately after leaving the heart, in other words,

when in the arteries, than it was a short time before passing into either, in other words, when it was in the veins;

and if attention be given, it will be found that this difference is very marked only in the neighborhood of the heart;

and is not so evident in parts more remote from it. In the next place, the consistency of the coats of which the

arterial vein and the great artery are composed, sufficiently shows that the blood is impelled against them with

more force than against the veins. And why should the left cavity of the heart and the great artery be wider and

larger than the right cavity and the arterial vein, were it not that the blood of the venous artery, having only been in

the lungs after it has passed through the heart, is thinner, and rarefies more readily, and in a higher degree, than

the blood which proceeds immediately from the hollow vein? And what can physicians conjecture from feeling

the pulse unless they know that according as the blood changes its nature it can be rarefied by the warmth of the

heart, in a higher or lower degree, and more or less quickly than before? And if it be inquired how this heat is

communicated to the other members, must it not be admitted that this is effected by means of the blood, which,

passing through the heart, is there heated anew, and thence diffused over all the body? Whence it happens, that

if the blood be withdrawn from any part, the heat is likewise withdrawn by the same means; and although the

heart were as-hot as glowing iron, it would not be capable of warming the feet and hands as at present, unless it

continually sent thither new blood. We likewise perceive from this, that the true use of respiration is to bring

sufficient fresh air into the lungs, to cause the blood which flows into them from the right ventricle of the heart,

where it has been rarefied and, as it were, changed into vapors, to become thick, and to convert it anew into

blood, before it flows into the left cavity, without which process it would be unfit for the nourishment of the fire that

is there. This receives confirmation from the circumstance, that it is observed of animals destitute of lungs that

they have also but one cavity in the heart, and that in children who cannot use them while in the womb, there is a

hole through which the blood flows from the hollow vein into the left cavity of the heart, and a tube through which it

passes from the arterial vein into the grand artery without passing through the lung. In the next place, how could

digestion be carried on in the stomach unless the heart communicated heat to it through the arteries, and along

with this certain of the more fluid parts of the blood, which assist in the dissolution of the food that has been

taken in? Is not also the operation which converts the juice of food into blood easily comprehended, when it is

considered that it is distilled by passing and repassing through the heart perhaps more than one or two hundred

times in a day? And what more need be adduced to explain nutrition, and the production of the different humors

of the body, beyond saying, that the force with which the blood, in being rarefied, passes from the heart towards

the extremities of the arteries, causes certain of its parts to remain in the members at which they arrive, and

there occupy the place of some others expelled by them; and that according to the situation, shape, or

smallness of the pores with which they meet, some rather than others flow into certain parts, in the same way

that some sieves are observed to act, which, by being variously perforated, serve to separate different species

of grain? And, in the last place, what above all is here worthy of observation, is the generation of the animal

spirits, which are like a very subtle wind, or rather a very pure and vivid flame which, continually ascending in

great abundance from the heart to the brain, thence penetrates through the nerves into the muscles, and gives

motion to all the members; so that to account for other parts of the blood which, as most agitated and

penetrating, are the fittest to compose these spirits, proceeding towards the brain, it is not necessary to

suppose any other cause, than simply, that the arteries which carry them thither proceed from the heart in the

most direct lines, and that, according to the rules of mechanics which are the same with those of nature, when

many objects tend at once to the same point where there is not sufficient room for all (as is the case with the

parts of the blood which flow forth from the left cavity of the heart and tend towards the brain), the weaker and

less agitated parts must necessarily be driven aside from that point by the stronger which alone in this way

reach it I had expounded all these matters with sufficient minuteness in the treatise which I formerly thought of

publishing. And after these, I had shown what must be the fabric of the nerves and muscles of the human body to

give the animal spirits contained in it the power to move the members, as when we see heads shortly after they

have been struck off still move and bite the earth, although no longer animated; what changes must take place in

the brain to produce waking, sleep, and dreams; how light, sounds, odors, tastes, heat, and all the other

qualities of external objects impress it with different ideas by means of the senses; how hunger, thirst, and the

other internal affections can likewise impress upon it divers ideas; what must be understood by the common

sense (sensuscommunis) in which these ideas are received, by the memory which retains them, by the fantasy

which can change them in various ways, and out of them compose new ideas, and which, by the same means,

distributing the animal spirits through the muscles, can cause the members of such a body to move in as many

different ways, and in a manner as suited, whether to the objects that are presented to its senses or to its

internal affections, as can take place in our own case apart from the guidance of the will. Nor will this appear at

all strange to those who are acquainted with the variety of movements performed by the different automata, or

moving machines fabricated by human industry, and that with help of but few pieces compared with the great

multitude of bones, muscles, nerves, arteries, veins, and other parts that are found in the body of each animal.

Such persons will look upon this body as a machine made by the hands of God, which is incomparably better

arranged, and adequate to movements more admirable than is any machine of human invention. And here I

specially stayed to show that, were there such machines exactly resembling organs and outward form an ape or

any other irrational animal, we could have no means of knowing that they were in any respect of a different

nature from these animals; but if there were machines bearing the image of our bodies, and capable of imitating

our actions as far as it is morally possible, there would still remain two most certain tests whereby to know that

they were not therefore really men. Of these the first is that they could never use words or other signs arranged in

such a manner as is competent to us in order to declare our thoughts to others: for we may easily conceive a

machine to be so constructed that it emits vocables, and even that it emits some correspondent to the action

upon it of external objects which cause a change in its organs; for example, if touched in a particular place it

may demand what we wish to say to it; if in another it may cry out that it is hurt, and such like; but not that it

should arrange them variously so as appositely to reply to what is said in its presence, as men of the lowest

grade of intellect can do. The second test is, that although such machines might execute many things with equal

or perhaps greater perfection than any of us, they would, without doubt, fail in certain others from which it could

be discovered that they did not act from knowledge, but solely from the disposition of their organs: for while

reason is an universal instrument that is alike available on every occasion, these organs, on the contrary, need a

particular arrangement for each particular action; whence it must be morally impossible that there should exist in

any machine a diversity of organs sufficient to enable it to act in all the occurrences of life, in the way in which

our reason enables us to act. Again, by means of these two tests we may likewise know the difference between

men and brutes. For it is highly deserving of remark, that there are no men so dull and stupid, not even idiots, as

to be incapable of joining together different words, and thereby constructing a declaration by which to make their

thoughts understood; and that on the other hand, there is no other animal, however perfect or happily

circumstanced, which can do the like. Nor does this inability arise from want of organs: for we observe that

magpies and parrots can utter words like ourselves, and are yet unable to speak as we do, that is, so as to

show that they understand what they say; in place of which men born deaf and dumb, and thus not less, but

rather more than the brutes, destitute of the organs which others use in speaking, are in the habit of

spontaneously inventing certain signs by which they discover their thoughts to those who, being usually in their

company, have leisure to learn their language. And this proves not only that the brutes have less reason than

man, but that they have none at all: for we see that very little is required to enable a person to speak; and since a

certain inequality of capacity is observable among animals of the same species, as well as among men, and

since some are more capable of being instructed than others, it is incredible that the most perfect ape or parrot

of its species, should not in this be equal to the most stupid infant of its kind or at least to one that was

crack-brained, unless the soul of brutes were of a nature wholly different from ours. And we ought not to

confound speech with the natural movements which indicate the passions, and can be imitated by machines as

well as manifested by animals; nor must it be thought with certain of the ancients, that the brutes speak, although

we do not understand their language. For if such were the case, since they are endowed with many organs

analogous to ours, they could as easily communicate their thoughts to us as to their fellows. It is also very worthy

of remark, that, though there are many animals which manifest more industry than we in certain of their actions,

the same animals are yet observed to show none at all in many others: so that the circumstance that they do

better than we does not prove that they are endowed with mind, for it would thence follow that they possessed

greater reason than any of us, and could surpass us in all things; on the contrary, it rather proves that they are

destitute of reason, and that it is nature which acts in them according to the disposition of their organs: thus it is

seen, that a clock composed only of wheels and weights can number the hours and measure time more exactly

than we with all our skin.

I had after this described the reasonable soul, and shown that it could by no means be educed from the power of

matter, as the other things of which I had spoken, but that it must be expressly created; and that it is not sufficient

that it be lodged in the human body exactly like a pilot in a ship, unless perhaps to move its members, but that it

is necessary for it to be joined and united more closely to the body, in order to have sensations and appetites

similar to ours, and thus constitute a real man. I here entered, in conclusion, upon the subject of the soul at

considerable length, because it is of the greatest moment: for after the error of those who deny the existence of

God, an error which I think I have already sufficiently refuted, there is none that is more powerful in leading feeble

minds astray from the straight path of virtue than the supposition that the soul of the brutes is of the same nature

with our own; and consequently that after this life we have nothing to hope for or fear, more than flies and ants; in

place of which, when we know how far they differ we much better comprehend the reasons which establish that

the soul is of a nature wholly independent of the body, and that consequently it is not liable to die with the latter

and, finally, because no other causes are observed capable of destroying it, we are naturally led thence to judge

that it is immortal.

Chapter 6

Three years have now elapsed since I finished the treatise containing all these matters; and I was beginning to

revise it, with the view to put it into the hands of a printer, when I learned that persons to whom I greatly defer,

and whose authority over my actions is hardly less influential than is my own reason over my thoughts, had

condemned a certain doctrine in physics, published a short time previously by another individual to which I will

not say that I adhered, but only that, previously to their censure I had observed in it nothing which I could imagine

to be prejudicial either to religion or to the state, and nothing therefore which would have prevented me from

giving expression to it in writing, if reason had persuaded me of its truth; and this led me to fear lest among my

own doctrines likewise some one might be found in which I had departed from the truth, notwithstanding the

great care I have always taken not to accord belief to new opinions of which I had not the most certain

demonstrations, and not to give expression to aught that might tend to the hurt of any one. This has been

sufficient to make me alter my purpose of publishing them; for although the reasons by which I had been induced

to take this resolution were very strong, yet my inclination, which has always been hostile to writing books,

enabled me immediately to discover other considerations sufficient to excuse me for not undertaking the task.

And these reasons, on one side and the other, are such, that not only is it in some measure my interest here to

state them, but that of the public, perhaps, to know them.

I have never made much account of what has proceeded from my own mind; and so long as I gathered no other

advantage from the method I employ beyond satisfying myself on some difficulties belonging to the speculative

sciences, or endeavoring to regulate my actions according to the principles it taught me, I never thought myself

bound to publish anything respecting it. For in what regards manners, every one is so full of his own wisdom, that

there might be found as many reformers as heads, if any were allowed to take upon themselves the task of

mending them, except those whom God has constituted the supreme rulers of his people or to whom he has

given sufficient grace and zeal to be prophets; and although my speculations greatly pleased myself, I believed

that others had theirs, which perhaps pleased them still more. But as soon as I had acquired some general

notions respecting physics, and beginning to make trial of them in various particular difficulties, had observed

how far they can carry us, and how much they differ from the principles that have been employed up to the

present time, I believed that I could not keep them concealed without sinning grievously against the law by which

we are bound to promote, as far as in us lies, the general good of mankind. For by them I perceived it to be

possible to arrive at knowledge highly useful in life; and in room of the speculative philosophy usually taught in

the schools, to discover a practical, by means of which, knowing the force and action of fire, water, air the stars,

the heavens, and all the other bodies that surround us, as distinctly as we know the various crafts of our artisans,

we might also apply them in the same way to all the uses to which they are adapted, and thus render ourselves

the lords and possessors of nature. And this is a result to be desired, not only in order to the invention of an

infinity of arts, by which we might be enabled to enjoy without any trouble the fruits of the earth, and all its

comforts, but also and especially for the preservation of health, which is without doubt, of all the blessings of this

life, the first and fundamental one; for the mind is so intimately dependent upon the condition and relation of the

organs of the body, that if any means can ever be found to render men wiser and more ingenious than hitherto, I

believe that it is in medicine they must be sought for. It is true that the science of medicine, as it now exists,

contains few things whose utility is very remarkable: but without any wish to depreciate it, I am confident that

there is no one, even among those whose profession it is, who does not admit that all at present known in it is

almost nothing in comparison of what remains to be discovered; and that we could free ourselves from an infinity

of maladies of body as well as of mind, and perhaps also even from the debility of age, if we had sufficiently

ample knowledge of their causes, and of all the remedies provided for us by nature. But since I designed to

employ my whole life in the search after so necessary a science, and since I had fallen in with a path which

seems to me such, that if any one follow it he must inevitably reach the end desired, unless he be hindered

either by the shortness of life or the want of experiments, I judged that there could be no more effectual provision

against these two impediments than if I were faithfully to communicate to the public all the little I might myself

have found, and incite men of superior genius to strive to proceed farther, by contributing, each according to his

inclination and ability, to the experiments which it would be necessary to make, and also by informing the public

of all they might discover, so that, by the last beginning where those before them had left off, and thus connecting

the lives and labours of many, we might collectively proceed much farther than each by himself could do.

I remarked, moreover, with respect to experiments, that they become always more necessary the more one is

advanced in knowledge; for, at the commencement, it is better to make use only of what is spontaneously

presented to our senses, and of which we cannot remain ignorant, provided we bestow on it any reflection,

however slight, than to concern ourselves about more uncommon and recondite phenomena: the reason of

which is, that the more uncommon often only mislead us so long as the causes of the more ordinary are still

unknown; and the circumstances upon which they depend are almost always so special and minute as to be

highly difficult to detect. But in this I have adopted the following order: first, I have essayed to find in general the

principles, or first causes of all that is or can be in the world, without taking into consideration for this end

anything but God himself who has created it, and without educing them from any other source than from certain

germs of truths naturally existing in our minds In the second place, I examined what were the first and most

ordinary effects that could be deduced from these causes; and it appears to me that, in this way, I have found

heavens, stars, an earth, and even on the earth water, air, fire, minerals, and some other things of this kind,

which of all others are the most common and simple, and hence the easiest to know. Afterwards when I wished

to descend to the more particular, so many diverse objects presented themselves to me, that I believed it to be

impossible for the human mind to distinguish the forms or species of bodies that are upon the earth, from an

infinity of others which might have been, if it had pleased God to place them there, or consequently to apply

them to our use, unless we rise to causes through their effects, and avail ourselves of many particular

experiments. Thereupon, turning over in my mind I the objects that had ever been presented to my senses I

freely venture to state that I have never observed any which I could not satisfactorily explain by the principles had

discovered. But it is necessary also to confess that the power of nature is so ample and vast, and these

principles so simple and general, that I have hardly observed a single particular effect which I cannot at once

recognize as capable of being deduced in man different modes from the principles, and that my greatest

difficulty usually is to discover in which of these modes the effect is dependent upon them; for out of this difficulty

cannot otherwise extricate myself than by again seeking certain experiments, which may be such that their result

is not the same, if it is in the one of these modes at we must explain it, as it would be if it were to be explained in

the other. As to what remains, I am now in a position to discern, as I think, with sufficient clearness what course

must be taken to make the majority those experiments which may conduce to this end: but I perceive likewise

that they are such and so numerous, that neither my hands nor my income, though it were a thousand times

larger than it is, would be sufficient for them all; so that according as henceforward I shall have the means of

making more or fewer experiments, I shall in the same proportion make greater or less progress in the

knowledge of nature. This was what I had hoped to make known by the treatise I had written, and so clearly to

exhibit the advantage that would thence accrue to the public, as to induce all who have the common good of

man at heart, that is, all who are virtuous in truth, and not merely in appearance, or according to opinion, as well

to communicate to me the experiments they had already made, as to assist me in those that remain to be made.

But since that time other reasons have occurred to me, by which I have been led to change my opinion, and to

think that I ought indeed to go on committing to writing all the results which I deemed of any moment, as soon as

I should have tested their truth, and to bestow the same care upon them as I would have done had it been my

design to publish them. This course commended itself to me, as well because I thus afforded myself more

ample inducement to examine them thoroughly, for doubtless that is always more narrowly scrutinized which we

believe will be read by many, than that which is written merely for our private use (and frequently what has

seemed to me true when I first conceived it, has appeared false when I have set about committing it to writing),

as because I thus lost no opportunity of advancing the interests of the public, as far as in me lay, and since thus

likewise, if my writings possess any value, those into whose hands they may fall after my death may be able to

put them to what use they deem proper. But I resolved by no means to consent to their publication during my

lifetime, lest either the oppositions or the controversies to which they might give rise, or even the reputation,

such as it might be, which they would acquire for me, should be any occasion of my losing the time that I had set

apart for my own improvement. For though it be true that every one is bound to promote to the extent of his

ability the good of others, and that to be useful to no one is really to be worthless, yet it is likewise true that our

cares ought to extend beyond the present, and it is good to omit doing what might perhaps bring some profit to

the living, when we have in view the accomplishment of other ends that will be of much greater advantage to

posterity. And in truth, I am quite willing it should be known that the little I have hitherto learned is almost nothing

in comparison with that of which I am ignorant, and to the knowledge of which I do not despair of being able to

attain; for it is much the same with those who gradually discover truth in the sciences, as with those who when

growing rich find less difficulty in making great acquisitions, than they formerly experienced when poor in making

acquisitions of much smaller amount. Or they may be compared to the commanders of armies, whose forces

usually increase in proportion to their victories, and who need greater prudence to keep together the residue of

their troops after a defeat than after a victory to take towns and provinces. For he truly engages in battle who

endeavors to surmount all the difficulties and errors which prevent him from reaching the knowledge of truth, and

he is overcome in fight who admits a false opinion touching a matter of any generality and importance, and he

requires thereafter much more skill to recover his former position than to make great advances when once in

possession of thoroughly ascertained principles. As for myself, if I have succeeded in discovering any truths in

the sciences (and I trust that what is contained in this volume 1 will show that I have found some), I can declare

that they are but the consequences and results of five or six principal difficulties which I have surmounted, and

my encounters with which I reckoned as battles in which victory declared for me. I will not hesitate even to avow

my belief that nothing further is wanting to enable me fully to realize my designs than to gain two or three similar

victories; and that I am not so far advanced in years but that, according to the ordinary course of nature, I may

still have sufficient leisure for this end. But I conceive myself the more bound to husband the time that remains

the greater my expectation of being able to employ it aright, and I should doubtless have much to rob me of it,

were I to publish the principles of my physics: for although they are almost all so evident that to assent to them no

more is needed than simply to understand them, and although there is not one of them of which I do not expect

to be able to give demonstration, yet, as it is impossible that they can be in accordance with all the diverse

opinions of others, I foresee that I should frequently be turned aside from my grand design, on occasion of the

opposition which they would be sure to awaken.

It may be said, that these oppositions would be useful both in making me aware of my errors, and, if my

speculations contain anything of value, in bringing others to a fuller understanding of it; and still farther, as many

can see better than one, in leading others who are now beginning to avail themselves of my principles, to assist

me in turn with their discoveries. But though I recognize my extreme liability to error, and scarce ever trust to the

first thoughts which occur to me, yet-the experience I have had of possible objections to my views prevents me

from anticipating any profit from them. For I have already had frequent proof of the judgments, as well of those I

esteemed friends, as of some others to whom I thought I was an object of indifference, and even of some whose

malignancy and envy would, I knew, determine them to endeavor to discover what partiality concealed from the

eyes of my friends. But it has rarely happened that anything has been objected to me which I had myself

altogether overlooked, unless it were something far removed from the subject: so that I have never met with a

single critic of my opinions who did not appear to me either less rigorous or less equitable than myself. And

further, I have never observed that any truth before unknown has been brought to light by the disputations that are

practised in the schools; for while each strives for the victory, each is much more occupied in making the best of

mere verisimilitude, than in weighing the reasons on both sides of the question; and those who have been long

good advocates are not afterwards on that account the better judges.

As for the advantage that others would derive from the communication of my thoughts, it could not be very great;

because I have not yet so far prosecuted them as that much does not remain to be added before they can be

applied to practice. And I think I may say without vanity, that if there is any one who can carry them out that

length, it must be myself rather than another: not that there may not be in the world many minds incomparably

superior to mine, but because one cannot so well seize a thing and make it one's own, when it has been learned

from another, as when one has himself discovered it. And so true is this of the present subject that, though I have

often explained some of my opinions to persons of much acuteness, who, whilst I was speaking, appeared to

understand them very distinctly, yet, when they repeated them, I have observed that they almost always changed

them to such an extent that I could no longer acknowledge them as mine. I am glad, by the way, to take this

opportunity of requesting posterity never to believe on hearsay that anything has proceeded from me which has

not been published by myself; and I am not at all astonished at the extravagances attributed to those ancient

philosophers whose own writings we do not possess; whose thoughts, however, I do not on that account

suppose to have been really absurd, seeing they were among the ablest men of their times, but only that these

have been falsely represented to us. It is observable, accordingly, that scarcely in a single instance has any one

of their disciples surpassed them; and I am quite sure that the most devoted of the present followers of Aristotle

would think themselves happy if they had as much knowledge of nature as he possessed, were it even under the

condition that they should never afterwards attain to higher. In this respect they are like the ivy which never

strives to rise above the tree that sustains it, and which frequently even returns downwards when it has reached

the top; for it seems to me that they also sink, in other words, render themselves less wise than they would be if

they gave up study, who, not contented with knowing all that is intelligibly explained in their author, desire in

addition to find in him the solution of many difficulties of which he says not a word, and never perhaps so much

as thought. Their fashion of philosophizing, however, is well suited to persons whose abilities fall below

mediocrity; for the obscurity of the distinctions and principles of which they make use enables them to speak of

all things with as much confidence as if they really knew them, and to defend all that they say on any subject

against the most subtle and skillful, without its being possible for any one to convict them of error. In this they

seem to me to be like a blind man, who, in order to fight on equal terms with a person that sees, should have

made him descend to the bottom of an intensely dark cave: and I may say that such persons have an interest in

my refraining from publishing the principles of the philosophy of which I make use; for, since these are of a kind

the simplest and most evident, I should, by publishing them, do much the same as if I were to throw open the

windows, and allow the light of day to enter the cave into which the combatants had descended. But even

superior men have no reason for any great anxiety to know these principles, for if what they desire is to be able

to speak of all things, and to acquire a reputation for learning, they will gain their end more easily by remaining

satisfied with the appearance of truth, which can be found without much difficulty in all sorts of matters, than by

seeking the truth itself which unfolds itself but slowly and that only in some departments, while it obliges us, when

we have to speak of others, freely to confess our ignorance. If, however, they prefer the knowledge of some few

truths to the vanity of appearing ignorant of none, as such knowledge is undoubtedly much to be preferred, and,

if they choose to follow a course similar to mine, they do not require for this that I should say anything more than I

have already said in this discourse. For if they are capable of making greater advancement than I have made,

they will much more be able of themselves to discover all that I believe myself to have found; since as I have

never examined aught except in order, it is certain that what yet remains to be discovered is in itself more

difficult and recondite, than that which I have already been enabled to find, and the gratification would be much

less in learning it from me than in discovering it for themselves. Besides this, the habit which they will acquire, by

seeking first what is easy, and then passing onward slowly and step by step to the more difficult, will benefit

them more than all my instructions. Thus, in my own case, I am persuaded that if I had been taught from my youth

all the truths of which I have since sought out demonstrations, and had thus learned them without labour, I should

never, perhaps, have known any beyond these; at least, I should never have acquired the habit and the facility

which I think I possess in always discovering new truths in proportion as I give myself to the search. And, in a

single word, if there is any work in the world which cannot be so well finished by another as by him who has

commenced it, it is that at which I labour.

It is true, indeed, as regards the experiments which may conduce to this end, that one man is not equal to the

task of making them all; but yet he can advantageously avail himself, in this work, of no hands besides his own,

unless those of artisans, or parties of the same kind, whom he could pay, and whom the hope of gain (a means

of great efficacy) might stimulate to accuracy in the performance of what was prescribed to them. For as to

those who, through curiosity or a desire of learning, of their own accord, perhaps, offer him their services,

besides that in general their promises exceed their performance, and that they sketch out fine designs of which

not one is ever realized, they will, without doubt, expect to be compensated for their trouble by the explication of

some difficulties, or, at least, by compliments and useless speeches, in which he cannot spend any portion of

his time without loss to himself. And as for the experiments that others have already made, even although these

parties should be willing of themselves to communicate them to him (which is what those who esteem them

secrets will never do), the experiments are, for the most part, accompanied with so many circumstances and

superfluous elements, as to make it exceedingly difficult to disentangle the truth from its adjuncts- besides, he

will find almost all of them so ill described, or even so false (because those who made them have wished to see

in them only such facts as they deemed conformable to their principles), that, if in the entire number there should

be some of a nature suited to his purpose, still their value could not compensate for the time what would be

necessary to make the selection. So that if there existed any one whom we assuredly knew to be capable of

making discoveries of the highest kind, and of the greatest possible utility to the public; and if all other men were

therefore eager by all means to assist him in successfully prosecuting his designs, I do not see that they could

do aught else for him beyond contributing to defray the expenses of the experiments that might be necessary;

and for the rest, prevent his being deprived of his leisure by the unseasonable interruptions of any one. But

besides that I neither have so high an opinion of myself as to be willing to make promise of anything

extraordinary, nor feed on imaginations so vain as to fancy that the public must be much interested in my

designs; I do not, on the other hand, own a soul so mean as to be capable of accepting from any one a favor of

which it could be supposed that I was unworthy.

These considerations taken together were the reason why, for the last three years, I have been unwilling to

publish the treatise I had on hand, and why I even resolved to give publicity during my life to no other that was so

general, or by which the principles of my physics might be understood. But since then, two other reasons have

come into operation that have determined me here to subjoin some particular specimens, and give the public

some account of my doings and designs. Of these considerations, the first is, that if I failed to do so, many who

were cognizant of my previous intention to publish some writings, might have imagined that the reasons which

induced me to refrain from so doing, were less to my credit than they really are; for although I am not

immoderately desirous of glory, or even, if I may venture so to say, although I am averse from it in so far as I

deem it hostile to repose which I hold in greater account than aught else, yet, at the same time, I have never

sought to conceal my actions as if they were crimes, nor made use of many precautions that I might remain

unknown; and this partly because I should have thought such a course of conduct a wrong against myself, and

partly because it would have occasioned me some sort of uneasiness which would again have been contrary to

the perfect mental tranquillity which I court. And forasmuch as, while thus indifferent to the thought alike of fame

or of forgetfulness, I have yet been unable to prevent myself from acquiring some sort of reputation, I have

thought it incumbent on me to do my best to save myself at least from being ill-spoken of. The other reason that

has determined me to commit to writing these specimens of philosophy is, that I am becoming daily more and

more alive to the delay which my design of self-instruction suffers, for want of the infinity of experiments I require,

and which it is impossible for me to make without the assistance of others: and, without flattering myself so

much as to expect the public to take a large share in my interests, I am yet unwilling to be found so far wanting in

the duty I owe to myself, as to give occasion to those who shall survive me to make it matter of reproach against

me some day, that I might have left them many things in a much more perfect state than I have done, had I not

too much neglected to make them aware of the ways in which they could have promoted the accomplishment of

my designs.

And I thought that it was easy for me to select some matters which should neither be obnoxious to much

controversy, nor should compel me to expound more of my principles than I desired, and which should yet be

sufficient clearly to exhibit what I can or cannot accomplish in the sciences. Whether or not I have succeeded in

this it is not for me to say; and I do not wish to forestall the judgments of others by speaking myself of my

writings; but it will gratify me if they be examined, and, to afford the greater inducement to this I request all who

may have any objections to make to them, to take the trouble of forwarding these to my publisher, who will give

me notice of them, that I may endeavor to subjoin at the same time my reply; and in this way readers seeing both

at once will more easily determine where the truth lies; for I do not engage in any case to make prolix replies, but

only with perfect frankness to avow my errors if I am convinced of them, or if I cannot perceive them, simply to

state what I think is required for defense of the matters I have written, adding thereto no explication of any new

matte that it may not be necessary to pass without end from one thing to another.

If some of the matters of which I have spoken in the beginning of the "Dioptrics" and "Meteorics" should offend

at first sight, because I call them hypotheses and seem indifferent about giving proof of them, I request a patient

and attentive reading of the whole, from which I hope those hesitating will derive satisfaction; for it appears to

me that the reasonings are so mutually connected in these treatises, that, as the last are demonstrated by the

first which are their causes, the first are in their turn demonstrated by the last which are their effects. Nor must it

be imagined that I here commit the fallacy which the logicians call a circle; for since experience renders the

majority of these effects most certain, the causes from which I deduce them do not serve so much to establish

their reality as to explain their existence; but on the contrary, the reality of the causes is established by the reality

of the effects. Nor have I called them hypotheses with any other end in view except that it may be known that I

think I am able to deduce them from those first truths which I have already expounded; and yet that I have

expressly determined not to do so, to prevent a certain class of minds from thence taking occasion to build

some extravagant philosophy upon what they may take to be my principles, and my being blamed for it. I refer to

those who imagine that they can master in a day all that another has taken twenty years to think out, as soon as

he has spoken two or three words to them on the subject; or who are the more liable to error and the less

capable of perceiving truth in very proportion as they are more subtle and lively. As to the opinions which are

truly and wholly mine, I offer no apology for them as new, -- persuaded as I am that if their reasons be well

considered they will be found to be so simple and so conformed, to common sense as to appear less

extraordinary and less paradoxical than any others which can be held on the same subjects; nor do I even boast

of being the earliest discoverer of any of them, but only of having adopted them, neither because they had nor

because they had not been held by others, but solely because reason has convinced me of their truth.

Though artisans may not be able at once to execute the invention which is explained in the "Dioptrics," I do not

think that any one on that account is entitled to condemn it; for since address and practice are required in order

so to make and adjust the machines described by me as not to overlook the smallest particular, I should not be

less astonished if they succeeded on the first attempt than if a person were in one day to become an

accomplished performer on the guitar, by merely having excellent sheets of music set up before him. And if I

write in French, which is the language of my country, in preference to Latin, which is that of my preceptors, it is

because I expect that those who make use of their unprejudiced natural reason will be better judges of my

opinions than those who give heed to the writings of the ancients only; and as for those who unite good sense

with habits of study, whom alone I desire for judges, they will not, I feel assured, be so partial to Latin as to

refuse to listen to my reasonings merely because I expound them in the vulgar tongue.

In conclusion, I am unwilling here to say anything very specific of the progress which I expect to make for the

future in the sciences, or to bind myself to the public by any promise which I am not certain of being able to fulfill;

but this only will I say, that I have resolved to devote what time I may still have to live to no other occupation than

that of endeavoring to acquire some knowledge of Nature, which shall be of such a kind as to enable us

therefrom to deduce rules in medicine of greater certainty than those at present in use; and that my inclination is

so much opposed to all other pursuits, especially to such as cannot be useful to some without being hurtful to

others, that if, by any circumstances, I had been constrained to engage in such, I do not believe that I should

have been able to succeed. Of this I here make a public declaration, though well aware that it cannot serve to

procure for me any consideration in the world, which, however, I do not in the least affect; and I shall always hold

myself more obliged to those through whose favor I am permitted to enjoy my retirement without interruption than

to any who might offer me the highest earthly preferments.

END

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