| René Descartes |
| Renatus Cartesius, philosopher and scientist, born at La Haye France, 31 |
| March, 1596; died at Stockholm, Sweden, 11 February 1650. He studied at the |
| Jesuit college of La Flèche, one of the most famous schools of the time. In 1613 |
| he went to Paris, where he formed a lasting friendship with Father Mersenne, O. |
| F. M., and made the acquaintance of the mathematician Mydorge. He afterwards |
| enlisted in the armies of Maurice of Nassau, and of the Duke of Bavaria. On 10 |
| November, 1619, he felt a strong impulse to set aside the prejudices of his |
| childhood and of his environment, and to devote his life to the restoration of |
| human knowledge, which was then in a state of decadence; and for him this |
| mission took on quite a mystical character. He had a dream which he interpreted |
| as a revelation, and he became convinced that "it was the Spirit of Truth that |
| willed to open for him all the treasures of knowledge". After much journeying in |
| Brittany, Poitou, Switzerland, and Italy, he returned to Paris in 1625. There he |
| remained for two years during which it was his fortune to meet Cardinal Bérulle |
| who encouraged him in his scientific vocation. But as Paris offered neither the |
| peace nor the independence his work demanded, he set out in 1629 for Holland, |
| and there in the midst of a commercial people he enjoyed the advantage of living |
| as quietly as in a desert. From this retreat he gave to the world his "Discours de |
| la méthode" (1637), "Méditations" (1641), "Principes" (1644), and |
| "Passions"(l649). "Le Monde" had been completed in 1633, but the |
| condemnation of Galileo frightened Descartes who preferred to avoid all collision |
| with ecclesiastical authority. He deferred the publication of this clever work |
| without, however, losing hope of eventually bringing it out. In 1649, yielding to the |
| entreaties of Queen Christina, he went to Sweden, and died at Stockholm of |
| inflammation of the lungs. |
| Descartes' work is important rather because of its quality than of its quantity. Let |
| us see first of all wherein his method is new. He observed, as Bacon had already |
| done before him, that there is no question on which men agree. "There is |
| nothing", he says "so evident or so certain that it may not be controverted. |
| Whence then this widespread and deep-rooted anarchy? From the fact that our |
| inquiries are haphazard" (Règles pour la direction de l'esprit, 4e Règle). The first |
| problem, then, is to discover a scientific method. How is success in this difficult |
| task to be assured? To begin with, we must cease to rely on authority; and for |
| two principal reasons. "In whom can we trust" when "there is hardly a statement |
| made by one man, of which the opposite is not loudly supported by some other?" |
| And even "if all were agreed, the knowledge of their teaching would not suffice |
| us." "Had we by rote all the arguments of Plato and Aristotle, we should not be |
| any the more philosophers unless we were able to bring to bear on any given |
| question a solid judgment of our own. We should have indeed learned history but |
| not mastered a science" (3e Règle) Philosophy presupposes the understanding |
| of problems--and consequently its method cannot be external, it must be |
| essentially immanent. The true method is to seek for reasonable evidence and |
| the norm of such evidence is to be found in the science of mathematics |
| (Discours de la méthode, 2e partie). "It is not that arithmetic and geometry are |
| the only sciences to be learned, but that he who would progress on the road to |
| truth must not delay over any object about which he cannot have a certainty |
| equal to that given by arithmetical and geometrical demonstrations" (2e Règle). |
| Is everything, then, capable of being known in this way, and consequently can |
| human knowledge become the complete counterpart of reality? Descartes says |
| so over and over again; it is his controlling idea; and he endeavours to prove it |
| both from the nature of our thought and from the universal connexion of things. |
| The mind is equally intelligent however diverse the objects it considers; and |
| those objects because of their perfect enchainment are always equally |
| intelligible. There is, therefore, no question "so far removed from us as to be |
| beyond our reach or so deeply hidden that we cannot discover it", provided only |
| that we persevere and follow the right method (Disc. de la méth. 2e partie; 4e |
| Règle). Such is the rationalism of Descartes, surpassing even that of Plato, in |
| which under the name of "the Infinite" three-fourths of reality remains for ever |
| unknowable. How then is this mathematical evidence to be obtained. Two |
| methods, dangerous at once and sterile, must be avoided. We cannot build on |
| the experience of our senses; "for they are often deceptive", and consequently |
| need a control which they have not in themselves. Bacon was misled on this |
| point (2e Règle). Neither can we adopt the syllogistic method; for this is not, as |
| was formerly thought, a means of discovery. It is simply a process in which, two |
| terms being given, we find by means of a third that the former two are linked |
| together, i. e. that they have some common characteristic. Now if they have this |
| common characteristic it is useless to search for it with any light other than their |
| own. Let them pass under direct scrutiny; let their natures be studied, and in |
| time the common trait will reveal itself. This is the mind's straight road to |
| discovery, passing on from one idea to another without the aid of a third. The |
| syllogism is of no use until the discovery has been made; it simply serves the |
| purpose of exposition (14e Règle). There are but two ways leading to |
| mathematical evidence: intuition and deduction (3e Règle). Intuition "is the |
| conception formed by an attentive mind so clear and distinct that it admits of no |
| doubt: or what amounts to the same thing, it is the clear conception of a sound |
| and attentive mind, the product of unaided reason" (3e Règle). Intuition is not, |
| therefore, perception by the senses--it is an act of the understanding brought to |
| bear on an idea. The senses do not supply the object but merely the occasion. A |
| movement, for instance, awakens in us the idea of motion, and it is that idea we |
| must regard as the object of intuition. In very simple matters intuition acts |
| quickly; thus "everyone can know intuitively that he exists; that a triangle is |
| terminated by three angles, neither more nor less, and that a globe has but one |
| surface" (3e Règle; 12e Règle; Rép. aux deux objections). In the case of objects |
| more or less complex, intuition proceeds by way of analysis. Since it deals with |
| ideas, and ideas are but one aspect of thought, everything must be reduced to |
| clear and distinct elements, to ultimate or "indecomposable" parts. These |
| ultimate parts must be inspected one after another, until the object is exhausted, |
| "by passing from those that are easily known to those that are less easily |
| known" (6e Règle). In the long run everything will be spread out in full light. |
| Deduction is the process in which by a continuous movement of thought we draw |
| from a thing that we certainly know the conclusions that of necessity flow from it. |
| This procedure may be carried on in two ways. "If, for instance, after various |
| calculations I discover the relation between the quantities A and B, between B |
| and C, between C and D, and lastly between D and E, I do not yet know the |
| relation between A and E"; but I can infer it by retracting the several steps of the |
| series. This is the first form of deduction (7e Règle). There is a second form in |
| which, the connecting links of the series being too numerous to enter the mental |
| field of vision all at once, we are content to draw conclusions from the general |
| impression we have of the series (7e Règle). Deduction is an intellectual |
| process, but it differs from intuition by bringing in memory as a factor. And this is |
| noteworthy in view of the important role that memory plays in the Cartesian |
| explanation of certitude, and the desperate effort he makes to defend this |
| procedure. From the conspicuous place that reason holds in the Cartesian |
| method, one might infer that there was no room for experience. Nothing could be |
| less true. For Descartes, as for Bacon, the one purpose of science is utility. He |
| also expects from it a continual betterment of the conditions of human life, and |
| his hopes in that direction go very far, as, for instance, when he says of medicine |
| that in the end it would procure us the boon of immortality (Disc. de la méth. 6e |
| partie). And as he who wills the end wills the means also, Descartes accepts in |
| its entirety the experimental part of the Baconian method (letter to Mersenne, |
| 1631), and acts accordingly. He put himself in touch with all the experimental |
| work of his day (letter, April, 1632), urged others to take up research (letter to |
| Mersenne, 1632), and carried on experiments of his own that covered a wide |
| range of subjects: the weight of air (letter, 2 June, 1631), the laws of sound and |
| light (letter, 1633); the essential differences between oils, spirits, eaux-de-vie, |
| common waters, aquafortis, and salts. He dissected the heads of various |
| animals to show the workings of memory and imagination (cf. letters to |
| Mersenne, 1633 April, 1637; 13 November, 1639; 4 January, 1643, ed. Cousin, |
| Paris, 1826). There was hardly a fact that escaped this apologist of Reason nor |
| anything into whose hidden nature he did not inquire; even the "Chasse de Pan" |
| he followed with his accustomed ardour. |
| But if the mind, moving as it does in the realm of intelligible objects, have a |
| power of intuition sufficient to master them all, why these researches? Are they |
| not a hindrance rather than a help? Let deduction but go on to the end, and it |
| must assuredly attain that exhaustive knowledge which is the goal of |
| investigation, but such is not the case. Experiment helps reasoning in more |
| ways than one. It supplies the fact that calls forth in our intelligence the idea of |
| the problem to be solved. That idea once aroused, the intelligence takes hold of |
| it, and may produce many others, according to the nature of which experience |
| and reason play reciprocal, yet different, roles. The idea of a problem may be so |
| simple as to allow a mathematical deduction of the properties of the object in |
| question and nothing more. In this case experiment is called in only by way of |
| illustration, as happens, for instance, in the study of the laws of motion. (Cf. |
| Principes, 2e partie.) But again the idea of a problem may be so complex as to |
| suggest various hypotheses, since principles as a rule are so fruitful that we can |
| draw from them more than we see in the world around us. We must then choose |
| from among the hypotheses presented by the intellect that which corresponds |
| most nearly to the facts: and experiment is our only resource. It acts as a sort of |
| guide to rational deduction. It sets up, so to say, a number of sign-posts which |
| point out, at the cross-roads of logic the right direction to the world of facts. |
| Finally, we may be confronted with two or more hypotheses equally applicable to |
| the known facts, observations must then be multiplied until we discover some |
| peculiarity which determines our choice: and thus experiment becomes a real |
| means of verification (Principes, 4e partie.) In every case experiment is, as it |
| were, the matter, while calculation becomes the form. In the physical world there |
| is nothing but motion and extension, nothing but quantity. Everything can be |
| reduced to numerical proportions, and this reduction is the final object of |
| science. To understand means to know in terms of mathematics. When this final |
| stage is reached, intelligence and experience unite in closest bonds: the intellect |
| setting its seal on experience and endowing it with intelligibility. |
| Such is the method of Descartes. There remains to be seen what use he makes |
| of it. Recourse must be had to provisional doubt as the only means of |
| distinguishing the true from the false in the labyrinth of contradictory opinions |
| which are held in the schools and in the world at large. We must needs imitate |
| those builders who, in order to erect a lofty structure, begin by digging deep, so |
| that the foundations may be laid on the rock and solid ground (Remarques sur |
| les 7es objections, ed. Charpentier, Paris; cf. Disc. de la m´thode, 3e partie.) |
| And this provisional doubt goes very deep indeed. We may reject the evidence of |
| the senses for they are deceptive, "and it is but the part of prudence never to |
| trust absolutely what has once deceived us" (1re Méditation). We may even |
| question whether there be "any earth or sky or other extended body"; for, |
| supposing that nothing of the sort exist, I can still have the impression of their |
| existence as I had before; this is plain from the phenomena of madness and |
| dreams. What is more, the very simplest and clearest truths are not free from |
| suspicion." How do I know that God has not so arranged it that I am deceived |
| each time I add two and three together, or number the sides of a square, or form |
| some judgment still more simple, if indeed anything more simple can be |
| imagined" (3e Méditation). What then remains intact? One thing only, the fact of |
| my thought itself. But if I think it is because I exist, for from the one to the other |
| of these terms we pass by simple inspection-- Cogito, ergo sum: Behold the |
| long-sought rock on which the edifice of knowledge must be built (Disc. de la |
| méth., 4e partie, 2e Méd.). But how is this to be done? how are we to make our |
| way out of the abyss into which we have descended? By analysing the basic |
| fact, i. e. the content of our thought. I observe that, since my thought gropes |
| amid doubt, I must be imperfect: and this idea calls forth this other, viz. of a |
| being that is not imperfect, and therefore is perfect and infinite (Disc. de la méth., |
| 4e partie.) Let us consider this other idea. It must necessarily include existence |
| otherwise something would be wanting to it; it would not be perfect or infinite. |
| Therefore, God exists, and "I know no less clearly and distinctly that an actual |
| and eternal existence belongs to His nature than I know that whatever I can |
| demonstrate of any figure or number belongs truly to the nature of that figure or |
| number " (Disc. de la méth., 4e partie; 5e Médit.; Rép. aux premières obj.). |
| God, therefore, is known to us at the outset, the moment we take the trouble to |
| look into the nature of our own minds; and this is enough to eliminate the |
| hypothesis of an evil genius that would take pleasure in deceiving us; it is enough |
| also to secure the validity of all our deductions, whatever be their length, for "I |
| recognize that it is impossible that He should ever deceive me, since in all fraud |
| and deceit there is a certain imperfection" (4e Méd.). Otherwise how would this |
| idea of God be anything more than an idle fancy? It has immensity; it has infinity, |
| and therefore it must of itself be capable of existing. Spinoza, and after him |
| Hegel, will teach that the possible infolds, as it were, an essential tendency to |
| existence, and that this tendency is greater in proportion as the possible is |
| perfect. It is on this principle that they will build their vast synthetic systems. |
| Descartes anticipates them and when closely pressed he replies just as do |
| these later philosophers. (Rép. aux premières objections.) It is a fact worth |
| noting with reference to the genesis of modern systems. |
| The presence in us of this idea of God must also be explained; and here we find |
| a new ray of light. The objective reality of our ideas must have some cause, and |
| this is readily found when there is question of secondary qualities; these may be |
| illusory or they may result from the imperfection of our nature. The question also |
| can be solved without too much difficulty when it concerns primary qualities. May |
| not these arise perchance from some depth of my own mental being that is |
| beyond the control of my will? But such explanations are of no avail when we try |
| to account for the idea of a being infinite and perfect. I myself am limited, finite; |
| and from the finite, turn it about as we may, we can never derive the infinite the |
| lesser never gives us the greater (3e Méd. cf. Princ., 7e partie). Considered from |
| any and every point of view, the idea of God enlightens us as to His existence. |
| Whatever the manner of our questioning it gives us always from the depth of its |
| fulness the one reply, Ego sum qui sum. Since then the veracity of God Himself |
| guarantees our faculties in their natural exercise, we may go forward in our |
| inquiry; and the first question that meets us concerns the subject in which the |
| process of thought takes place, i.e. the soul. Understanding, conceiving, |
| doubting, affirming, denying, willing, refusing, imagining, feeling, desiring--these |
| are the activities of what I call my soul. Now all these activities have one |
| common quality: they cannot take place without thought or perception, without |
| consciousness or knowledge. Thought then is the essential attribute of the soul. |
| The soul is "a thing that thinks" (2e Méd., Princ., 1re partie) and it is nothing |
| else. There is no substratum underlying and supporting its various states; its |
| whole being issues in each of its activities; thought and soul are equivalent (12e |
| Règle). |
| Is thought, then, always in some mode of activity? Descartes leans to the belief |
| that it is. "I exist", he says, "but for how long? Just as long as I am thinking; for |
| perhaps if I should wholly cease to think, I should at the same time altogether |
| cease to be" (2e Méd.). It is only with reluctance and under the pressure of |
| objections that he concedes to the soul a simple potentia or power of thinking |
| (5es Obj.); and, as may be easily seen, the concession is quite illogical. |
| Thought, though in itself a unitary process, takes on different forms; it begins |
| with confused ideas or perceptions which require the co-operation of the body; |
| such are the feelings of pleasure and pain, sensations imagination, and local |
| memory. Then the soul has clear and distinct ideas, which it begets and |
| develops within itself as immanent activities. Under this head come the ideas of |
| substance, duration, number, order extension, figure, motion, thought, |
| intelligence, and will (6e Méd.; Princ., I). |
| These clear and distinct notions constitute of themselves the object of the |
| understanding, and one may say that they are all involved in the idea of perfect |
| being. Whether I understand, or pass judgment or reason, it is always that idea |
| which I perceive and my understanding could have no other object, seeing that its |
| sphere of action is always the infinite, the eternal and the necessary. To advance |
| in knowledge is to progress in the knowledge of God Himself. (Rep. aux 2es obj.) |
| But thought has another dominant form, viz. freedom. For Descartes this function |
| of the mind is a fact "of which reason can never convince us", but one which "we |
| experience in ourselves", and this fact is so evident" that it may be considered |
| one of the most generally known ideas" (Rep. aux 3es obj.; Rep. aux 5es obj.- |
| Princ., 1re partie). Not only is this freedom a primordial and undeniable datum of |
| consciousness: it is, in a way, infinite like God, "since there is no object to |
| which it cannot turn". (4e Méd.; Princ., 1re partie.) It does not creep round in a |
| sort of semi-ignorance, as St. Thomas Aquinas holds, but it grows as the |
| influencing motives become clearer; indifference is but its lowest stage (letter to |
| Mersenne, 20 May, 1630). The part it plays in our lives is considerable: it enters |
| into each of our judgments, and it is the formal cause of all our errors. It makes |
| itself felt in every part of our organism, and through this it influences the external |
| world. Nevertheless, the sum total of motion in the world is always constant; for |
| while our wills may change the direction of movement they do not affect its |
| quantity. (Letter to Regius.) Confronting the soul is the external world: but the |
| soul does not see it as it really is. Heat, odour taste, light, sound, resistance, |
| weight are qualities which we attribute to bodies but which are really in ourselves, |
| since we only conceive them in relation to ourselves. In reality there is nothing in |
| the physical world but motion and extension. Motion imitates as far as possible |
| the immutability of God who is its first cause; hence its principal laws, viz. that |
| the sum of motion in the world is always constant; that a body will continue in its |
| actual state unless disturbed by some other body outside itself; that "once a |
| body is in motion we have no reason for thinking its present velocity will ever |
| cease provided it impinges on no other body which would slacken or destroy its |
| motion". All movement is primarily rectilinear (on this point Aristotle was |
| mistaken). When two bodies moving in different directions collide, a change |
| takes place in their directions, but "such change is always the least possible". |
| When two moving bodies impinge on each other, one cannot transmit any motion |
| to the other without losing what it transmits (Princ., 2e partie). Extension is not |
| infinite in duration but it is infinite in space. "It seems to me that one cannot |
| prove or even conceive that there are limits to the matter of which the world is |
| composed, for I find it is composed of nothing but extension in length, breadth, |
| and depth. So that whatever possesses these three dimensions is a portion of |
| such matter": and however far back in imagination we push the limits of space |
| we still find these three dimensions; they are bounded by no limits (letter to |
| Chanut; letter to Marus). Extension is therefore one block, continuous from end |
| to end; and this proves at the same time that there is no such thing as a |
| vacuum, either in bodies or between them. Moreover extension is divisible ad |
| infinitum since the divided particles, however small, are still extended. It is |
| everywhere homogeneous, since it is made up of spatial dimensions only, and |
| these of themselves give rise to no qualitative differences. And this brilliant idea |
| suggested to Descartes many hypotheses that were to prove fruitful. In his view |
| the matter of the earth and of the stars was the same; and spectrum analysis |
| subsequently proved that he was correct. He held that the primordial state of the |
| sun and planets was nebulous, that under the influence of a cooling process the |
| heavenly bodies formed their crusts, and to changes in these crusts is due the |
| variation in brilliance of the stars and the emergence of the continents on our |
| earth. (Cf. Traité du Monde; Princ., 3e and 4e p.) It does not follow that the world |
| is self-sufficient; but the finality, of which so much is said, leads to nothing. God |
| gave matter a first impulse and the rest followed in the course of nature's laws. |
| "Even if the chaos of the poets be granted, one could always show that, thanks |
| to the laws of nature, this confusion would eventually work itself out to our |
| present order"; the laws of nature being such that "matter is constrained to pass |
| through all the forms of which it is capable". |
| The older Descartes grew, the more he busied himself with morals, and his aim |
| was to end up with a treatise on ethics. As a matter of fact, we have his treatise |
| on the passions, and a few brief disquisitions scattered among his letters to |
| Chanut and to the Princess Elizabeth. The passions are perceptions generated |
| and nurtured in the soul "through the medium of the nerves" (Passions, 1re |
| partie, art. 3-22). The nerves are bundles of fine threads: these threads contain |
| the animal spirits which are the subtlest parts of the blood: and they all meet at |
| the pineal gland which is the seat of the soul. By means of this mechanism the |
| thinking subject receives impressions from the world without, perceives them, |
| and transforms them into passions (Pass., 1re p, art. 31). And though our |
| organism thus contains the cause of our passions, it is not their subject either |
| entirely or partially; on this point also Aristotle was mistaken. There are |
| perceptions arising from the body and localizing themselves in one or other |
| portion of it--such as hunger, thirst, pain--but the passions are different. They |
| originate in the body, but belong to the soul alone; they are purely psychological |
| facts (Passions, 1re p., art.25). There are as many passions as there are ways |
| in which objects capable of affecting our senses may be hurtful or profitable to |
| us. The primary passions to which all others may be reduced are the six |
| following: |
| admiration or surprise, produced by an object as to which we are as yet |
| ignorant whether it is useful or hurtful; |
| love and hate, caused by the impression produced on our organs of sense |
| by objects which are already known to us as beneficial or harmful; |
| desire, which is but the love or the hate we bear an object considered as |
| future; |
| joy and sadness, which result from the presence of an object that is loved |
| or hated (Passions, 2e partie, art. 52). |
| Perhaps on the whole St. Thomas and Bossuet will be found to have surpassed |
| Descartes, by reducing all the passions to love. In the Cartesian teaching the |
| passions are good in themselves, but they must be kept in subjection to the law |
| of moral order. What this law is he does not clearly indicate; he gives only some |
| scattered precepts in which one may discern a noble effort to build up a |
| Stoico-Christian system of ethics. |
| The foregoing account may perhaps give the impression that Descartes was a |
| great savant rather than a great philosopher; but the significance of his scientific |
| work should be properly understood. What remains of value is not so much his |
| theories, but the impetus given by his genius, his method, his discoveries. His |
| quantitative conception of the world is being gradually abandoned, and today |
| men's minds are turning to a philosophy of nature wherein quality plays a |
| controlling part. |
| Clodius Piat |
| Transcribed by Rick McCarty |
| The Catholic Encyclopedia, Volume IV |
| Copyright © 1908 by Robert Appleton Company |
| Online Edition Copyright © 1999 by Kevin Knight |
| Nihil Obstat. Remy Lafort, Censor |
| Imprimatur. +John M. Farley, Archbishop of New York |
| The Catholic Encyclopedia: NewAdvent.org |
| * * * * * * |
| Enciclopedia Catolica: EnciclopediaCatolica.com |