Authors born between 1665 and 1700 CE
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The Search for Knowledge
Rules for Investigation
I Think, Therefore I am
Truth in Clarity and Distinctness
Publication and Experiment
A Thinking Thing
What is Clearly Apprehended
Material Things and Imagination
Origins of Sensations
Passions of the Soul
The Connection in the Brain
Joy and Cheerfulness
René Descartes (1596-1650) was born at La Haye, Touraine, France. He was educated at the Jesuit school of La Flèche between 1604 and 1612, after which went to Paris. He withdrew into mathematical studies between 1614 and 1616, then emerged to enlist in the army of Prince Maurice of Orange, probably because it gave him a means of "considering the manners of other men" (extract 2). In 1619 he volunteered for military service in Bavaria. About this time, he had the inspiration that led to the method he developed for solving philosophical and scientific problems. He quit military service in 1621, returning to France where, by selling some property, he was able to invest the proceeds to obtain a yearly income.
By 1629, Descartes had decided to devote himself entirely to philosophical speculation, moving to Holland and living there for 20 years. During this time he wrote a great many letters dealing with physics, musical theory, and mathematics, mostly addressed to his friend Mersenne in Paris. Descartes rarely based his thoughts on the heritage of the past, preferring instead to carry out scientific experiments and pursue knowledge through his own meditations. He pursued an analytical technique, breaking complex subjects into their elementary parts. Science he compared to a tree with metaphysics as its root, physics as its trunk, and morals, medicine, and mechanics as its branches. He thought the universe was infinite and that the earth traveled around the sun. He suppressed these ideas after the persecution of Galileo and also injected a great deal of pious observations about God into his published work, avoiding open conflict with church doctrine, although the proof he offered for the existence of God was not appreciated.
In 1637 he described his approach to solving problems in his Discourse on the Method of Rightly Directing One’s Reason and of Seeking the Truth in the Sciences. This book also contained philosophical essays on coordinate geometry, optics, and meteors. In 1641 he published Meditations on First Philosophy. These works were well received in some philosophical circles and universities, and a group of adherents to Cartesian theory emerged. They often gave a more energetic presentation of his views than Descartes anticipated. In one instance he was summoned before the magistrates of Utrecht to defend himself against accusations of irreligion and slander. Fortunately, he was protected by the French ambassador and the Prince of Orange. In 1644 his Principles of Philosophy appeared in Utrecht, dealing with laws of motion, a theory of planetary orbits based on vortices, and with heat light, and other physical effects. Passions of the Soul appeared in 1649, expressing Descartes views on the relationship between the mind and the body, and on perceptions, feelings, and emotions.
Descartes initially put forward a skeptical approach to philosophy and science, accepting no prior knowledge unless convinced it was free from error. In this way he decided that the only sure knowledge he had was that he could think and that this proved that he existed. Examination of his thinking soul convinced him that it was not extended in space like matter. He therefore postulated a form of dualism whereby mind and body were totally different substances but interacted in some way—through the pineal gland in the brain. These two features of his thought—skepticism and the dualism of his mind-body theory—became an integral part of Western philosophy in subsequent centuries. His invention of coordinate geometry became a powerful technique adopted by mathematicians.
In 1649 Descartes left Holland to take up a position in the court of the Queen of Sweden. This was an unfortunate move for a man who pursued warmth with a passion and had the habit of spending most of the morning in bed. The queen demanded he give her an hour of philosophical instruction every day at the frigid Swedish hour of 5 am. He died of pneumonia that winter.
The following extracts touch on some of the main points of his thought. As the original publications sometimes exist in both Latin and French, there may be alternative translations into English, which are indicated in parentheses.
1 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 ardently desired instruction. But as soon as I had finished the entire course of study at school, 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.
Discourse on Method, 1
2 It is true that, while busied only in considering the manners of other men, I found there, too, scarce any ground for settled conviction. I observed hardly less contradiction among them than in the opinions of the philosophers. So that the greatest advantage I derived from their study consisted in this—that, observing many things which, however extravagant and ridiculous they appear to us, are yet by common consent received and approved by other great nations, I learned to entertain little regard for the truth of that 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. I decided 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.
Discourse on Method, 1
3 Among the branches of philosophy, I had at an earlier period given some attention to logic and to the mathematics of geometrical analysis and algebra—three arts or sciences which should, I thought, contribute something to my design. But on examination I found that, as for logic, its syllogisms and the majority of its other precepts are useful in communicating what we already know—or even, as in the art of Lully, in speaking without judgment of things we are ignorant of—rather than in the investigation of the unknown. And although this science does indeed contain 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.
What then of the analysis of the ancients and the algebra of the moderns—apart from the fact that they embrace only matters highly abstract and apparently 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. The latter is so completely subject to certain rules and formulas that it yields an art full of confusion and obscurity—calculated to embarrass—instead of a science fitted to cultivate the mind.
Discourse on Method, 2
4 By these considerations I was induced to seek some other method which would contain the advantages of these three and be exempt from their defects. A multitude of laws often only hampers justice—so that a state is best governed with few laws that are rigidly administered. Therefore, in like manner, instead of the great number of precepts that make up logic, 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 as true that I did not clearly know to be such. That is to say, to carefully avoid hasty judgment and prejudice—to include nothing more in my judgment 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 pursue my thoughts by starting with objects simplest and easiest to know, so that I might ascend little by little—by gradations, as it were—to knowledge of more complex things, even if this meant thinking about things in an order different from the way they normally appear.
The last, in every case to make enumerations so complete and reviews so general, that I might be sure that nothing was omitted.
Discourse on Method, 2
5 I had long ago noticed that, in common affairs, it is sometimes necessary to adopt—as if above doubt—opinions that we know are highly uncertain, as I said earlier. But as I now desired to give my attention solely to the search after truth, I thought that a procedure exactly the opposite was called for. That is, I ought to reject as absolutely false all opinions in regard to which I could suppose the least ground for doubt, in order to discover whether after that there remained anything in my belief that was wholly certain. Accordingly, seeing that our senses sometimes deceive us, I was willing to suppose that nothing that they presented to us really existed. And because some men make mistakes in reasoning, and fall into fallacious arguments—even on the simplest matters of geometry—I saw that I was as open to error as any other. I therefore rejected as false all lines of reasoning I had previously taken to be true. Finally, I considered that the very same thoughts and perceptions which we experience when awake may also be experienced when we are asleep, even though at that time not one of them is true. So I assumed that all the thoughts and perceptions that had ever entered into my mind when awake had no more truth in them than the illusions of my dreams.
Discourse on Method, 4
6 But immediately upon this I observed that, while I wished in this way to think that everything was false, it was absolutely necessary that I, who was thinking that, should have some form of existence. I observed that this truth—I think, therefore I am—was so certain and so evident that no grounds for doubt capable of shaking it, however extravagant, could be put forward by skeptics. I concluded that I might, without scruple, accept this as the first principle of the philosophy I was searching for.
Discourse on Method, 4
7 In the next place, I attentively examined what I was. 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 I could not therefore suppose that I was not. 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. On the other hand, if I had merely ceased to think, I would have had no reason to believe that I existed, even if all the other objects that I had ever imagined had really existed. I therefore concluded that I was a substance whose whole essence or nature consists only in thinking, and that to exist it has need of no place, nor is dependent on any material things. Thus I— that is to say, the soul by which I am what I am—exist wholly distinct from the body, and can be even more easily known than the latter, and as such would still continue to be all that is, even if the latter did not exist.
Discourse on Method, 4
8 After this I inquired in general into what is essential 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 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 conceive very clearly that in order to think it is necessary to exist. Therefore I concluded that I might take, as a general rule, the principle that all things 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.
Discourse on Method, 4
9 I had after this described the rational soul, and shown that it could by no means be derived 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.
Discourse on Method, 5
10 Three years have now elapsed since I finished the treatise containing all these matters [some scientific theories were included in the Discourse on the Method]. 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 [Galileo]. I will not say that I adhered to such doctrine, 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. 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 demonstration, and not to give expression to anything that might tend to offend any one. This has been sufficient to make me alter my decision to publish . . .
Discourse on Method, 6
11 But as soon as I had acquired some general notions respecting physics I began to test them in various particular problems, and 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 we can, the general good of mankind. For by these notions in physics I perceived it to be possible to arrive at knowledge highly useful in life. In place of the speculative philosophy usually taught in the schools, it would be possible to discover a practical approach. By means of this, 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 to promote 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. This 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 are ever to 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 a 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.
Discourse on Method, 6
12 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 some reflection, however slight—than to concern ourselves about more uncommon and recondite phenomena. The reason for this 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. . .
Thereupon, turning over in my mind all 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 I 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 many different ways from the principles. My greatest difficulty usually is to discover on which of these ways the effect is dependent. I cannot extricate myself from this difficulty other than by again undertaking certain experiments, which may be such that their results are not the same if we explain it one way, than if we explain it in another. As to what remains, I think I am now in a position to discern with sufficient clearness the course to take to make the majority of those experiments resolve these matters. But I also perceive 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. Thus, to the extent that I shall have the means of making more or fewer experiments, I shall in the same proportion make greater less progress in the knowledge of nature.
Discourse on Method, 6
13 But what, then, am I? A thinking thing, it has been said. But what is a thinking thing? It is a thing that doubts, understands (conceives), affirms, denies, wills, refuses, that imagines also, and perceives. Assuredly it is not little, if all these properties belong to my nature. But why should they not belong to it? Am I not that very being who now doubts of almost everything; who, for all that, understands and conceives certain things; who affirms one alone as true, and denies the others; who desires to know more of them, and does not wish to be deceived; who imagines many things, sometimes even despite his will; and is likewise percipient of many, as if through the medium of the senses. . .
Is there also any one of these attributes that can be properly distinguished from my thought, or that can be said to be separate from myself? For it is of itself so evident that it is I who doubt, I who understand, and I who desire, that it is here unnecessary to add anything by way of rendering it more clear. And I am as certainly the same being who imagines; for, although it may be (as I before supposed) that nothing I imagine is true, still the power of imagination does not cease really to exist in me and to form part of my thoughts. To sum up, I am the same being who perceives, that is, who apprehends certain objects as by the organs of sense, since in truth I see light, hear a noise, and feel heat.
14 But, in conclusion, I find I have insensibly reverted to the point I desired; for, since it is now manifest to me that bodies themselves are not properly perceived by the senses nor by the faculty of imagination, but by the intellect alone; and since they are not perceived because they are seen and touched, but only because they are understood (or rightly comprehended by thought), I readily discover that there is nothing more easily or dearly apprehended than my own mind.
15 I am a thinking (conscious) thing, that is, a being who doubts, affirms, denies, knows a few objects, and is ignorant of many—(who loves, hates), wills, refuses—who imagines likewise, and perceives. For, as I before remarked, although the things that I perceive or imagine are perhaps nothing at all apart from me and in themselves, I am nevertheless assured that those modes of consciousness which I call perceptions and imaginations—in as far only as they are modes of consciousness—exist in me. And in the little I have said I think I have summed up all that I really know, or at least all that up to this time I was aware I knew.
Now, as I am endeavoring to extend my knowledge more widely, I will use circumspection, and consider with care whether I can still discover in myself anything further that I have not yet observed. I am certain that I am a thinking thing; but do I not therefore likewise know what is required to render me certain of a truth? In this first knowledge, doubtless, there is nothing that gives me assurance of its truth except the clear and distinct perception of what I affirm. This would not indeed be sufficient to give me the assurance that what I say is true, if it could ever happen that anything I thus clearly and distinctly perceived should prove false. And accordingly it seems to me that I may now take as a general rule, that all that is very clearly and distinctly apprehended (conceived) is true.
16 As belonging to the class of things that are clearly apprehended, I recognize the following, namely, magnitude or extension in length, breadth, and depth; figure, which arises from the termination of extension; situation, which bodies of diverse figures preserve with reference to each other; and motion, or the change of situation; to which may be added substance, duration, and number. But with regard to light, colors, sounds, odors, tastes, heat, cold and the other tactile qualities, they appear in thought with so much obscurity and confusion, that I cannot determine even whether they are true or false—in other words, whether or not the ideas I have of these qualities are in truth the ideas of real objects. For although I before remarked that formal falsity, or falsity under its right name, can be met with only in judgments, there may nevertheless be found in ideas a certain material falsity, which arises when they represent nothing as if it were something.
Thus, for example, the ideas I have of cold and heat are so far from being clear and distinct, that I am unable from them to discover whether cold is only the absence of heat, or heat the absence of cold; or whether they are or are not real qualities. And since, ideas being as it were images, there can be none that does not seem to us to represent some object, the idea which represents cold as something real and positive will not improperly be called false if it is correct to say that cold is nothing but an absence of heat; and similarly in other cases. To ideas of this kind, indeed, it is not necessary that I should assign any author besides myself. For if they are false, that is, represent objects that are unreal, the natural light teaches me that they proceed from nothing. In other words, that they are in me only because something is missing in the perfection of my nature. But if these ideas are true, yet because they exhibit so little reality to me that I cannot even distinguish the object represented from non-being, I do not see why I should not be the author of them.
17 With reference to those ideas of corporeal things that are clear and distinct, there are some which, as appears to me, might have been taken from the idea I have of myself, as those of substance, duration, number, and the like. For when I think that a stone is a substance, or a thing capable of existing of itself, I realize that I am likewise a substance. However, I also conceive that I am a thinking and non-extended thing. The stone, on the contrary, is extended and unconscious. There is thus the greatest diversity between the two concepts. Yet these two ideas seem to have this in common: that they both represent substances. In the same way, when I think of myself as now existing, and recollect besides that I existed some time ago, and when I am conscious of various thoughts whose number I know, I then acquire the ideas of duration and number, which I can afterwards transfer to as many objects as I please. With respect to the other qualities that go to make up the ideas of corporeal objects, namely, extension, figure, situation, and motion, it is true that they are not formally in me, since I am merely a thinking being. But because they are only certain modes of substance, and because I myself am a substance, it seems possible that they may be contained in me immanently.
18 There now only remains the inquiry as to whether material things exist. With regard to this question, I at least know with certainty that such things may exist—in as far as they constitute the object of the pure mathematics, since, regarding them in this aspect, I can conceive them clearly and distinctly. . . Further, the faculty of imagination which I possess, and am conscious of when I apply myself to the consideration of material things, is sufficient to persuade me of their existence. For, when I attentively consider what imagination is, I find that it is simply a certain application of the cognitive faculty to a body that is immediately present to it, and which therefore exists.
19 And to render this quite clear, I can point, in the first place, to the difference that exists between imagination and pure intellection (or conception). For example, when I imagine a triangle I not only conceive that it is a figure made up of three lines, but also, at the same time, look upon these three lines as present by the power and internal application of my mind, and this is what I call imagining. But if I desire to think of a chiliagon, I indeed rightly conceive that it is a figure composed of a thousand sides, as easily as I conceive that a triangle is a figure composed of only three sides; but I cannot imagine the thousand sides of a chiliagon as I do the three sides of a triangle. Nor so to speak, can I view them as present (with the eyes of my mind). . .Thus I observe that a special effort of mind is necessary for the act of imagination, which is not required to conceiving or understanding. And this special exertion of mind clearly shows the difference between imagination and pure intellection
20 . . . merely because I know with certitude that I exist, and because, in the meantime, I do not observe that anything necessarily belongs to my nature or essence beyond my being a thinking thing, I rightly conclude that my essence consists only in my being a thinking thing (or a substance whose whole essence or nature is merely thinking). And yet I may assert, as I will shortly claim, that I certainly do possess a body with which I am very closely conjoined. Nevertheless, because, on the one hand, I have a clear and distinct idea of myself—in as far as I am only a thinking and unextended thing—and as, on the other hand, I possess a distinct idea of body—in as far as it is only an extended and unthinking thing—it is certain that I (that is, my mind, by which I am what I am) is entirely and truly distinct from my body, and may exist without it.
21 But there is nothing which that nature teaches me more expressly (or with more impact on the senses) than that I have a body that is affected adversely when I feel pain, and stands in need of food and drink when I experience the sensations of hunger and thirst, etc. And therefore I ought not to doubt that there is some truth in such information.
Nature likewise teaches me by these sensations of pain, hunger, thirst, etc., that I am not only lodged in my body as a pilot in a vessel, but that I am besides so intimately conjoined and, as it were, intermixed with it, that my mind and body compose a certain unity. For if this were not the case, I would not feel pain when my body is hurt—seeing I am merely a thinking thing—but would perceive the wound by the understanding alone, just as a pilot perceives by sight when any part of his vessel is damaged. And when my body needs food or drink, I would have a clear knowledge of this, and not be made aware of it by the confused sensations of hunger and thirst. For, in truth, all these sensations of hunger, thirst, pain, etc., are nothing more than certain confused modes of thinking, arising from the union and apparent fusion of mind and body.
22 But nature, taking the term in the sense explained, teaches me to shun what causes in me the sensation of pain, and to pursue what affords me the sensation of pleasure, and other things of this sort. But I do not discover that it teaches me, in addition to this, from these diverse perceptions of the senses, to draw any conclusions respecting external objects without previous (careful and mature) consideration of them by the mind. For it appears to me that it is the function of the mind alone—and not of the composite whole of mind and body—to discern the truth in those matters. Thus, although the impression a star makes on my eye is not larger than that from the flame of a candle, I do not, nevertheless, experience any real or positive impulse causing me to believe that the star is not greater than the flame. The fact is merely that I have judged it so from my youth without any rational justification. And, though on approaching the fire I feel heat—even pain on approaching it too closely—I have, however, from this no ground for holding that something resembling the heat I feel is in the fire, any more than that there is something there similar to the pain. All that I have ground for believing is that there is something in it, whatever it may be, which excites in me those sensations of heat or pain.
23 Besides this, nature teaches me that my own body is surrounded by many other bodies, some of which I have to seek, and others to shun. And indeed, as I perceive different sorts of colors, sounds, odors, tastes, heat, hardness, etc., I can safely conclude that there are in the bodies from which the diverse perceptions of the senses proceed, certain variations that give rise to them, although, perhaps, not in reality like them. And since, among these diverse perceptions of the senses, some are agreeable, and others disagreeable, there can be no doubt that my body, or rather my entire self—in as far as I am composed of body and mind—may be variously affected, both beneficially and hurtfully, by surrounding bodies.
24 To commence this examination accordingly, I here remark, in the first place, that there is a vast difference between mind and body, in respect that body, from its nature, is always divisible, and that mind is entirely indivisible. For in truth, when I consider the mind—that is, when I consider myself in so far only as I am a thinking thing—I can distinguish in myself no parts, but I very clearly discern that I am something absolutely one and entire. And although the whole mind seems to be united to the whole body, yet, when a foot, an arm, or any other part is cut off, I am conscious that nothing has been taken from my mind. Furthermore, the faculties of willing, perceiving, conceiving, etc., cannot properly be called its parts, for the same mind is exercised (all entire) in willing, in perceiving, and in conceiving, etc. But quite the opposite holds in corporeal or extended things. For I cannot imagine any one of them (no matter how small it may be) that I cannot easily divide in thought, and which, therefore, I do not know to be divisible. This would be sufficient to teach me that the mind or soul of man is entirely different from the body, if I had not already been apprised of it on other grounds.
I remark, in the next place, that the mind does not immediately receive the impression from all the parts of the body, but only from the brain, or perhaps even from one small part of it, namely, that in which the common sense is said to be. This, as often as it is affected in the same way, gives rise to the same perception in the mind, although meanwhile the other parts of the body may be diversely disposed—as is proved by innumerable experiments, which it is unnecessary here to enumerate.
25 I remark, finally, that each movement made in the part of the brain by which the mind is immediately affected impresses it with only a single sensation. The most likely supposition in the circumstances is that this movement causes the mind to experience, among all the sensations that it is capable of impressing upon it, the one that is the best fitted and generally the most useful for the preservation of the human body when it is in full health. . . Thus, for example, when the nerves of the foot are violently or more than usually shaken, the motion passing through the medulla of the spine to the innermost parts of the brain affords a sign to the mind from which it experiences a sensation, namely, of pain, as if it were in the foot, by which the mind is admonished and excited to do its utmost to remove the cause of it as dangerous and hurtful to the foot. . . In the same way, when we stand in need of drink, there arises from this want a certain parchedness in the throat that moves its nerves, and by means of them the internal parts of the brain. And this movement affects the mind with the sensation of thirst, because there is nothing on that occasion which is more useful for us than to be made aware that we have need of drink for the preservation of our health; and so in other instances.
26 And certainly this consideration is of great service, not only in enabling me to recognize the errors to which my nature is liable, but likewise in rendering it more easy to avoid or correct them. For I know that all my senses more usually indicate to me what is true than what is false, in matters relating to the advantage of the body. And I am able almost always to make use of more than a single sense in examining the same object. Besides this, being able to use my memory in connecting present with past knowledge—and having an understanding that has already discovered all the causes of my errors—I ought no longer to fear that the daily presentation of the senses is deceptive. And I ought to reject all the doubts of those bygone days as hyperbolical and ridiculous, especially the general uncertainty respecting sleep, which I could not distinguish from the waking state. For I now find a very marked difference between the two states, in respect that our memory can never connect our dreams with each other and with the course of life, in the way it is in the habit of doing with events that occur when we are awake. . .
But when I perceive objects with regard to which I can distinctly determine both the place whence they come, and that in which they are, and the time at which they appear to me, and when, without interruption, I can connect the perception I have of them with the whole of the other parts of my life, I am perfectly sure that what I thus perceive occurs while I am awake and not during sleep. And I ought not in the least degree to doubt of the truth of those presentations, if, after having called together all my senses, my memory, and my understanding for the purpose of examining them, no information comes from any one of these faculties that contradicts that of any other . . . But because the necessities of action frequently oblige us to come to a determination before we have had leisure for so careful an examination, it must be confessed that the life of man is frequently subject to error with respect to individual objects. And we must, in conclusion, acknowledge the weakness of our nature.
27 There is nothing in which the defective nature of the sciences which we have received from the ancients appears more clearly than in what they have written on the passions. For, although this is a matter which has at all times been the object of much investigation, and though it would not appear to be one of the most difficult (inasmuch as since every one has experience of the passions within himself), there is no necessity to borrow one's observations from elsewhere in order to discover their nature. Yet that which the ancients have taught regarding them is both so slight—and for the most part so far from credible—that I am unable to entertain any hope of approximating to the truth excepting by shunning the paths which they have followed. This is why I shall be here obliged to write just as though I were treating a matter that no one had ever touched on before me.
To begin with, I consider that all that which occurs or that happens anew is by the philosophers, generally speaking, termed a passion, in as far as the subject to which it occurs is concerned, and an action in respect of him who causes it to occur. Thus although the agent and the recipient are frequently very different, the action and the passions are always one and the same thing, although having different names, because of the two diverse subjects to which it may be related.
Passions of the Soul, 1
28 . . . it is easy to recognize that there is nothing in us which we ought to attribute to our soul excepting our thoughts, which are mainly of two sorts: one being the actions of the soul and the other its passions. Those which I call its actions are all our desires, because we find by experience that they proceed directly from our soul, and appear to depend on it alone. On the other hand, we may usually term one's passions all those kinds of perception or forms of knowledge which are found in us, because it is often not our soul which makes them what they are, and because it always receives them from the things which are represented by them.
The Passions of the Soul, 17
29 After having considered in what the passions of the soul differ from all its other thoughts, it seems to me that we may define them generally as the perceptions, feelings, or emotions of the soul which we relate specially to it, and which are caused, maintained, and fortified by some movement of the animal spirits [described in 31].
The Passions of the Soul, 27
30 Next, I note also that we do not observe the existence of any subject which more immediately acts upon our soul than the body to which it is joined, and that we must consequently consider that what in the soul is passion is in the body commonly speaking an action. Thus there is no better means of arriving at a knowledge of our passions than to examine the difference which exists between soul and body in order to know to which of the two we must attribute each one of the functions which are within us. . . As to this we shall not find much difficulty if we realize that all that we experience as being in us—and may be observed to exist in wholly inanimate bodies—must be attributed to our body alone. And, on the other hand, that all that which is in us and which we cannot in any way conceive as possibly pertaining to a body, must be attributed to our soul.
The Passions of the Soul, 2-3
31 Thus because we have no conception of the body as thinking in any way, we have reason to believe that every kind of thought which exists in us belongs to the soul. And because we do not doubt there are inanimate bodies which can move in as many as or in more diverse modes than can ours, and which have as much heat or more (experience demonstrates this to us in flame, which of itself has much more heat and movement than any of our members), we must believe that all the heat and all the movements which are in us pertain only to body, inasmuch as they do not depend on thought at all. . . We know finally that all the movements of the muscles, as also of the senses, depend on the nerves, which resemble small filaments, or little tubes, which all proceed from the brain, and thus contain like it certain very subtle air or wind which is called the animal spirits.
The Passions of the Soul, 4
32 But in order to understand all these things more perfectly, we must know that the soul is really joined to the whole body, and that we cannot, properly speaking, say that it exists in any one of its parts to the exclusion of the others, because  it is one and in some manner indivisible, owing to the disposition of its organs, which are so related to one another that when any one of them is removed, that renders the whole body defective; because  the soul is of a nature which has no relation to extension, nor dimensions, nor other properties of the matter of which the body is composed, but only to the whole conglomerate of its organs—as appears from the fact that we could not in any way conceive of the half or the third of a soul, nor of the space it occupies; and because  it does not become smaller owing to the cutting off of some portion of the body, but separates itself from it entirely when the union of its assembled organs is dissolved.
The Passions of the Soul, 30
33 It is likewise necessary to know that although the soul is joined to the whole body, there is a certain part in which it exercises its functions more particularly than in all the others. And it is usually believed that this part is the brain, or possibly the heart: the brain, because it is with it that the organs of sense are connected, and the heart because it is apparently there that we experience the passions. But, in examining the matter with care, it seems as though I had clearly ascertained that the part of the body in which the soul exercises its functions immediately is in nowise the heart. Nor is it the whole of the brain, but merely the most inward part—that is, a certain very small gland [the pineal] which is situated in the middle of its substance. This is suspended above the duct whereby the animal spirits in its anterior cavities have communication with those in the posterior, so that the slightest movements which take place in it may alter very greatly the course of these spirits. And, reciprocally, the smallest changes which occur in the course of the spirits may do much to change the movements of this gland.
The Passions of the Soul, 31
34 Joy is an agreeable emotion of the soul consisting of the enjoyment that the soul possesses in the good that the impressions of the brain represent to it as it own. I say that it is in this emotion that the enjoyment of the good consists; for as a matter of fact the soul receives no other fruits from all the good things that it possesses. And as it has no joy in these, it may be said that it does not enjoy them more than if it did not possess them at all.
I add that it is of the good that the impressions of the brain represent to it as its own in order not to confound this joy, which is a passion, with the joy that is purely intellectual and comes into the soul by the action of the soul alone. This last we may call an agreeable emotion excited in the soul in which the enjoyment is of that good which its understanding represents as its own. It is true that while the soul is united to the body this intellectual joy can hardly fail to be accompanied by that which is a passion. For as soon as our understanding perceives that we possess some good thing—even although this good may be so different from all that pertains to body that it is not in the least capable of being imagined—imagination does not fail immediately to make some impression in the brain from which proceeds the movement of the spirits which excites the passion of joy.
The Passions of the Soul, 91
35 Finally, what I call cheerfulness is a species of joy in which there is this peculiarity—that its sweetness is increased by the recollection of the evils which we have suffered, and of which we are relieved, in the same way as we feel freed of some heavy burden that we have for a long time borne on our shoulders.
The Passions of the Soul, 210
1-26 Adapted from The Method, Meditations and Selections from the Principles of Descartes, translated by J. Veitch, Edinburgh and London, 1907.
27-35 Adapted from The Philosophical works of Descartes, rendered into English by Elizabeth S. Haldane and G. R. T. Ross, volume I, Cambridge University Press, England, 1911.
Authors born between 1665 and 1700 CE
Introduction and selection of extracts Copyright © Rex Pay 2003