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Descartes, René Du perron

Descartes, René Du perron

(b. La Haye, Touraine, France, 31 March 1596; d. Stockholm, Sweden, 11 February 1650)

natural philosophy, scientific method, mathematics, optics, mechanics, physiology.

Fontenelle, in the eloquent contrast made in his Éloge de Newton, described Descartes as the man who “tried in one bold leap to put himself at the source of everything, to make himself master of the first principles by means of certain clear and fundamental ideas, so that he could then simply descend to the phenomena of nature as to necessary consequences of these principles.” This famous characterization of Descartes as the theoretician who “set out from what he knew clearly, in order to find the cause of what he saw,” as against Newton the experimenter, who “set out from what he saw, in order to find the cause,” has tended to dominate interpretations of both these men who “saw the need to carry geometry into physics.”1

Descartes was born into the noblesse de robe, whose members contributed notably to intellectual life in seventeenth-century France. His father was conseiller to the Parlement of Brittany; from his mother he received the name du Perron and financial independence from property in Poitou. From the Jesuits of La Flèche he received a modern education in mathematics and physics—including Galileo’s telescopic discoveries—as well as in philosophy and the classics, and there began the twin domination of imagination and geometry over his precocious mind. He described in an early work, the Olympica, how he found “in the writings of the poets weightier thoughts than in those of the philosophers. The reason is that the poets wrote through enthusiasm and the power of imagination.” The seeds of knowledge in us, “as in a flint were” brought to light by philosophers “through reason; struck out through imagination by poets they shine forth more brightly.”2 Then, after graduating in law from the University of Poitiers, as a gentleman volunteer in the army of Prince Maurice of Nassau in 1618 he met Isaac Beeckman at Breda. Beeckman aroused him to self-discovery as a scientific thinker and mathematician and introduced him to a range of problems, especially in mechanics and acoustics, the subject of his first work, the Compendium musicae of 1618; published posthumously in 1650. On 26 March 1619 he reported to Beeckman his first glimpse of “an entirely new science,”3 which was to become his analytical geometry.

Later in the year, on 10 November, then in the duke of Bavaria’s army on the Danube, he had the experience in the famous poêle (lit. “stove,” “well-heated room”), claimed to have given direction to the rest of his life. He described in the Discours de la mèthode how, in a day of solitary thought, he reached two radical conclusions: first, that if he were to discover true knowledge he must carry out the whole program himself, just as a perfect work of art or architecture was always the work of one master hand; second, that he must begin by methodically doubting everything taught in current philosophy and look for self-evident, certain principles from which to reconstruct all the sciences. That night, according to his seventeenthcentury biographer Adrien Baillet, these resolutions were reinforced by three consecutive dreams. He found himself, first, in a street swept by a fierce wind, unable to stand, as his companions were doing, because of a weakness in his right leg; second, awakened by a clap of thunder in a room full of sparks; and third, with a dictionary, then a book in which he read Quid vitae sectabor iter? (“What way of life shall I follow?”), then verses presented by an unknown man beginning Est et non; he recognized the Latin as the opening lines of two poems by Ausonius. Before he finally awoke he had interpreted the first dream as a warning against past errors, the second as the descent of the spirit of truth, and the third as the opening to him of the path to true knowledge. However this incident may have been elaborated in the telling, it symbolizes both the strength and the hazards of Descartes’s unshakable confidence and resolve to work alone. But he did not make his vision his life’s mission for another nine years, during which (either before or after his tour of Italy from 1623 to 1625) he met Mersenne, who was to become his lifelong correspondent, and took part in scientific meetings in Paris. The next decisive incident, according to Baillet, was a public encounter in 1628 in which he demolished the unfortunate Chandoux by using his method to distinguish sharply between true scientific knowledge and mere probability. Among those present was the influential Cardinal de Bérulle, who a few days later charged him to devote his life to working out the application of “his manner of philosophizing... to medicine and mechanics. The one would contribute to the restoration and conservation of health, and the other to some diminution and relief in the labours of mankind.”4 To execute this design he withdrew, toward the end of the year, to the solitary life in the Netherlands which he lived until his last journey to Stockholm in 1649, where, as Queen Christina’s philosopher, he died in his first winter.

The primarily centrifugal direction of Descartes’s thought, moving out into detailed phenomena from a firm central theory (in contrast with the more empirical scientific style of Francis Bacon and Newton), is shown by the sequence of composition of his major writings. He set out his method in the Rules for the Direction of the Mind, left unfinished in 1628 and published posthumously, and in the Discours de la méthode, written in the Netherlands along with the Météores, La dioptrique, and La géométrie, which he presented as examples of the method. All were published in one volume in 1637. At the same time his investigation into the true ontology led him to the radical division of created existence into matter as simply extended substance, given motion at the creation, and mind as unextended thinking substance. This conclusion he held to be guaranteed by the perfection of God, who would not deceive true reason. How these two mutually exclusive and collectively exhaustive categories of substance could have any interaction in the embodied soul that was a man was a question discussed between Gassendi, Hobbes, and Descartes in the Objections and Replies published with his Meditations on First Philosophy in 1641.

It was from these first principles that he had given an account in Le monde, ou Traité de la lumière of cosmogony and cosmology as products simply of matter in motion, making the laws of motion the ultimate “laws of nature” and all scientific explanation ultimately mechanistic. This treatise remained unpublished in Descartes’s lifetime. So too did the associated treatise L’homme, in which he represented animals and the human body as sheer mechanisms, an idea already found in the Rules. He withheld these essays, on the brink of publication, at the news of Galileo’s condemnation in 1633, and instead published his general system of physics, with its Copernicanism mitigated by the idea that all motion is relative, in the Principles of Philosophy in 1644. Finally, he brought physiological psychology within the compass of his system in Les passions de l’âme in 1649. This system aimed to be as complete as Aristotle’s, which it was designed to replace. It was not by chance that it dealt in the same order with many of the same phenomena (such as the rainbow), as well as with others more recently investigated (such as magnetism).

A comparison of Descartes’s performance with his program of scientific method presents a number of apparent contradictions. He made much of the ideal of a mathematically demonstrated physics, yet his fundamental cosmology was so nearly entirely qualitative that he came to fear that he had produced nothing more than a beautiful “romance of nature.”5 His planetary dynamics was shown by Newton to be quantitatively ridiculous. He wrote in the Discours, “I noticed also with respect to experiments [expériences] that they become so much the more necessary, the more we advance in knowledge,”6 yet his fundamental laws of nature, the laws of motion and impact, had to be dismantled by Huygens and Leibniz for their lack of agreement with observation. These apparent contradictions may be resolved in the contrast between Descartes’s theoretical ideal of completed scientific knowledge and the actual process and circumstances of acquiring such knowledge. For the modern reader to pay too much attention to his mechanics and to the Principles, a premature conception of completed science, can obscure Descartes’s firm grasp of the necessity for observation and experiment already expressed in the Rules in his criticism “of those philosophers who neglect experiments and expect truth to rise from their own heads like Minerva from Jupiter’s.”7

No other great philosopher, except perhaps Aristotle, can have spent so much time in experimental observation. According to Baillet, over several years he studied anatomy, dissected and vivisected embryos of birds and cattle, and went on to study chemistry. His correspondence from the Netherlands described dissections of dogs, cats, rabbits, cod, and mackerel; eyes, livers, and hearts obtained from an abattoir; experiments on the weight of the air and on vibrating strings; and observations on rainbows, parahelia, and other optical phenomena. Many of his scientific writings reflect these activities and show sound experimental knowledge, although the extreme formalism of his physiological models obscures the question of his actual knowledge of some aspects of anatomy. Attention to the whole range of his scientific thought and practice shows a clear conception not only of completed scientific knowledge but also of the roles of experiment and hypothesis in making discoveries and finding explanations by which the body of scientific knowledge was built up.

Descartes’s conception of completed scientific knowledge was essentially that envisaged by Aristotle’s true scientific demonstration. It was the geometers’ conception of a system deduced from selfevident and certain premises. He wrote

In physics I should consider that I knew nothing if I were able to explain only how things might be, without demonstrating that they could not be otherwise. For, having reduced physics to mathematics, this is something possible, and I think that I can do it within the small compass of my knowledge, although I have not done it in my essays.8

His optimism about the possibility of achieving such demonstrations seems to have depended on which end of the chain of reasoning he was contemplating. When considering the results of his analysis reducing created existence to extension (with motion) and thought, he seems to have been confident that it would be possible to show that from these “simple natures” the composite observed world must follow. It may be argued that his treatment of motion failed just where his a priori confidence led him to suppose that his analysis (of what was soon seen to be an insufficient range of data) placed his first principles beyond the need for empirical test. But when considering the chain lower down, nearer this complex world, he was more hesitant. He wrote to Mersenne:

You ask me whether I think what I have written about refraction is a demonstration. I think it is, at least as far as it is possible, without having proved the principles of physics previously by metaphysics, to give any demonstration on this subject... as far as any other question of mechanics, optics, or astronomy, or any other question which is not purely geometrical or arithmetical, has ever been demonstrated. But to demand that I should give geometrical demonstrations of matters which depend on physics is to demand that I should do the impossible. If you restrict the use of “demonstration”to geometrical proofs only, you will be obliged to say that Archimedes demonstrated nothing in mechanics, nor Vitellio in optics, nor Ptolemy in astronomy, etc., which is not commonly maintained. For, in such matters, one is satisfied that the writers, having presupposed certain things which are not obviously contradictory to experience, have besides argued consistently and without logical fallacy, even if their assumptions are not exactly true.9

The paradox of Descartes as a natural scientist is that his grasp improved the more hopeless he found the immediate possibility of deducing solutions of detailed problems from his general first principles. Standing amidst the broken sections of a chain that he could not cast up to heaven, the experimentalist and constructor of hypothetical models came to life. In Descartes’s letter prefaced to the French translation of the Principles (1647), he wrote that two, and only two, conditions determined whether the first principles proposed could be accepted as true: “First they must be so clear and evident that the mind of man cannot doubt their truth when it attentively applies itself to consider them”; and secondly, everything else must be deducible from them. But he went on to admit,“It is really only God alone who has perfect wisdom, that is to say, who has a complete knowledge of the truth of all things.”10 To find the truth about complex material phenomena man must experiment, but as the sixth part of the Discours shows, the need to experiment was an expression of the failure of the ideal.

As well as being demonstrative, scientific knowledge had to be explanatory; for Descartes the two went together. He wrote, “I have described... the whole visible world as if it were only a machine in which there was nothing to consider but the shapes and movements [of its parts].”11 To such a mechanism it was possible to apply mathematics and calculation, but it was the mechanism that explained. His insistence that even mathematical science without fundamental explanations was insufficient appears in his interestingly similar criticisms of Harvey for starting simply with a beating heart in explaining the circulation of the blood and of Galileo for likewise failing to reduce the mathematical laws of moving bodies to their ultimate mechanisms. He commented on the latter that “without having considered the first causes of nature, he has only looked for the reasons for certain particular effects, and that thus he has built without foundation.”12 By this insistence Descartes here again extracted from the failure of his ideal a fundamental contribution to scientific thinking. He became the first great master to make the hypothetical model, or “conjecture,” a systematic tool of research.

Current natural philosophy accepted Aristotle’s absolute ontological distinction between naturally generated bodies (inanimate and animate) and artificial things made by man. Hence, in principle no humanly constructed imitation or model could throw real light on the naturally endowed essence and cause of behavior. This distinction had become blurred in the partial mechanization of nature made by some philosophers. Descartes’s innovation was to assert the identity of the synthesized artificial construction with the naturally generated product and to make this identification an instrument of scientific research:

And certainly there are no rules in mechanics that do not hold also in physics, of which mechanics forms a part or species [so that all artificial things are at the same time natural]: for it is not less natural for a clock, made of these or those wheels, to indicate the hours, than for a tree which has sprung from this or that seed to produce a particular fruit. Accordingly, just as those who apply themselves to the consideration of automata, when they know the use of some machine and see some of its parts, easily infer from these the manner in which others which they have not seen are made, so, from the perceptible effects and parts of natural bodies, I have endeavoured to find out what are their imperceptible causes and parts.13

This reduction made the principles of the mechanistic model the only principles operating in nature, thus bringing the objectives of the engineer into the search for the nature of things and throwing the entire world of matter open to the same form of scientific inquiry and explanation. Research, whether into cosmology or physiology, was reduced to the discovery and elucidation of mechanisms. He could construct in distant space the imaginary world of Le monde and L’homme, and later the world of the Principles, as explicitly and unambiguously hypothetical imitations of our actual world, made in accordance with the known laws of mechanics. The heuristic power of the model was that, like any other theory advanced in anticipation of facts, its own properties suggested new questions to put to nature. The main issue in any historical judgment of Descartes here is not whether his own answers were correct but whether his questions were fruitful. In insisting that experiment and observation alone could show whether the model corresponded with actuality, he introduced further precision into his theory of demonstration.

Descartes used the word demonstrer to cover both the explanation of the observed facts by the assumed theory and the proof of the truth of the theory. When challenged with the criticism that this might make the argument circular, he replied by contrasting two kinds of hypothesis.14 In astronomy various geometrical devices, admittedly false in nature, were employed to yield true conclusions only in the sense that they “saved the appearances.” But physical theories were proposed as true. He was persuaded of the truth of the assumption that the material world consisted of particles in motion by the number of different effects he could deduce, as diverse as the operation of vision, the properties of salt, the formation of snow, the rainbow, and so on. Thus he made range of application the empirical criterion of truth. He wrote in the Discours:

If some of the matters of which I have spoken in the beginning of the Dioptrique and the Météores should, at first sight, shock people because I have called them suppositions, and do not seem to bother about their proof, let them have the patience to read them carefully right through, and I hope that they will find themselves satisfied. For it seems to me that the reasonings are so interwoven that as the later ones are demonstrated by the earlier which are their causes, these earlier ones are reciprocally demonstrated by the later which are their effects. And it must not be thought that in this I commit the fallacy which logicians call arguing in a circle, for, since experience renders the majority of these effects very certain, the causes from which I deduce them do not so much serve to prove them as to explain them; on the other hand, the causes are proved by the effects.15

The test implied precisely by the criterion of range of confirmation was the experimentum crucis. This is the most obvious feature in common between Descartes’s logic of experiment and that of Francis Bacon. Descartes described its function in the Discours:

Reviewing in my mind all the objects that have ever been presented to my senses, I venture truly to say that I have not there observed anything that I could not satisfactorily explain by the principles I had discovered. But I must also confess that the power of nature is so ample and so vast and that these principles are so simple and so general, that I have observed hardly any particular effect that I could not at once recognize to be deducible from them in several different ways, and that my greatest difficulty is usually to discover in which of these ways it depends on them. In such a case, I know no other expedient than to look again for experiments [expériences] such that their result is not the same if it has to be explained in one of these ways as it would be if explained in the other.16

It was a logician rather than an experimenter who seems to have been uppermost in Descartes’s application of this criterion in the same way to very general assumptions, such as the corpuscularian natural philosophy, and to questions as particular as whether the blood left the heart in systole or in diastole. Descartes argued in La description du corps humain (1648–1649) that whereas Harvey’s theory that the blood was forced out of the heart by a muscular contraction might agree with the facts observed so far, “that does not exclude the possibility that all the same effects might follow from another cause, namely from the dilatation of the blood which I have described. But in order to be able to decide which of these two causes is true, we must consider other observations which cannot agree with both of them.”17 Harvey replied in his Second Disquisition to Jean Riolan.

As the great optimist of the scientific movement of the seventeenth century, Descartes habitually wrote as if he had succeeded in discovering the true principles of nature to such an extent that the whole scientific program was within sight of completion. Then, as Seth Ward neatly put it, “when the operations of nature shall be followed up to their staticall (and mechanicall) causes, the use of induction will cease, and syllogisme succeed in place of it.” But Descartes would surely have agreed with Ward’s qualification that “in the interim we are to desire that men have patience not to lay aside induction before they have reason.”18


1. Fontenelle, Oeuvres diverses, new ed., III (The Hague, 1729), 405–406.

2. Part of the Olympica incorporated in the Cogitationes privatae (1619–1621); see Oeuvres, X, 217.

3.Oeuvres, X, 156.

4. Baillet. II, 165.

5.Ibid., preface, p. xviii.

6.Oeuvres, VI, 63.

7. Rule V: see Oeuvres, X, 380.

8. Letter to Mersenne, 11 Mar. 1640; see Oeuvres, III, 39. The “Essays” were the volume of 1637.

9. Letter to Mersenne, 27 May 1638; see Oeuvres, II, 141–142.

10.Oeuvres, IX. pt. 2, 2–3.

11.Principia philosophiae, IV, 188; Oeuvres, VIII, pt. 1, 315 (Latin);IX, pt. 2, 310 (French, alone with passage in square brackets).

12. Letter to Mersenne, 11 Oct. 1638; see Oeuvres, II, 380. For his comments on Harvey, see Discours V.

13.Principia philosophiae, IV, 203; Oeuvres, VIII, pt. 1, 326 (Latin); IX, pt. 2, 321–322 (French, alone with passage in square brackets).

14. Letter to J.-B. Morin, 13 July 1638; see Oeuvres, II, 197–202; cf. his letters to Vatier, 22 Feb. 1638, ibid., I, 558–565, and to Mersenne, I Mar. 1638, ibid., II, 31–32.

15.Oeuvres, VI, 76.

16.Ibid., pp. 64–65; cf. Principia philosophiae, III, 46; VIII. pt. 2,100–101; and IX, pt. 2, 124–125.

17.Oeuvres, XI, 241–242; cf. the comments on this controversy by J. B. Duhamel, “Quae sit cordis motus effectrix causa,” in Philosophia vetus et nova. II, Physica generalis, III.ii.2 (Paris,1684), 628–631.

18.Vindiciae academiarum (Oxford, 1654), p. 25.


Descartes’s complete works can be found in Oeuvres de Descartes, C. Adam and P. Tannery, eds. 12 vols. (Paris,1897–1913), together with the revised Correspondence, C. Adam and G. Milhaud, eds. (Paris, 1936–). Besides these, primary sources for Descartes’s life are Adrien Baillet, La vie de Monsieur Descartes, 2 vols. (Paris, 1691), which should be read with C. Adam, Vie et oeuvres de Descartes (in Oeuvres, XII); Isaac Beeckman, Journal tenu... de 1604 à 1634, C. de Waard, ed., 3 vols. (The Hague,1939–1953): Marin Mersenne, Correspondance, C. de Waard, R. Pintard, B. Rochot, eds. (Paris, 1932–).

For Descartes’s philosophy and method and their background, see E. Gilson, Index scolastico-cartésien (Paris,1912); Études sur le rôle de la pensée médiévale dans la formation du système cartésien (Paris, 1930); Discours de la méthode: texte et commentaire (Paris, 1947); Alexandre Koyré, Entretiens sur Descartes (Paris-New York, 1944); G. Milhaud, Descartes savant (Paris, 1921); L. Roth, Descartes’ Discourse on Method (Oxford, 1937); H. Scholz, A. Kratzer, and J. E. Hofmann, Descartes (Münster, 1951); and Norman Kemp Smith, New Studies in the Philosophy of Descartes (London, 1952).

Specific aspects of Descartes’s scientific method are discussed in A. Gewirtz, “Experience and the Non-mathematical in the Cartesian Method,” in Journal of the History of Ideas, 2 (1941), 183–210; and A. C. Crombie,“Some Aspects of Descartes’ Attitude to Hypothesis and Experiment,” in Académie Internationale d’Histoire des Sciences, Actes du Symposium International des Sciences Physiques et Mathématiques dans la Première Moitié du XVIIe Siècle: Pise-Vinci, 16–18 Juin 1958 (Paris, 1960), pp. 192–201. An indispensable bibliography is G. Sebba, Descartes and His Philosophy: A Bibliographical Guide to the Literature, 1800–1958 (Athens, Ga., 1959).

A. C. Crombie

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Descartes, Rene Du Perron


(b. La Haye, Touraine, France, 31 March 1596;

d. Stockholm, Sweden, 11 February 1650), natural philosophy, scientific method, mathematics, optics, mechanics, physiology. For the original article on Descartes see DSB, vol. 4.

Since the 1970s there has been enormous interest in Descartes’s scientific thought. There have been numerous new studies of his physics and its foundations, and its relation to scholastic thought about the physical world. Recent studies have emphasized the systematic nature of Descartes’s scientific thought, and the way in which the various pieces of his thought fuse to make a unified whole. Also, as historians come to understand the period better, they have come to see what is distinctively Cartesian in this point of view, and how Descartes’s scientific thought differs radically from that of other contemporaries, such as Galileo.

Natural Philosophy . In both Le monde, ou Traité de la lumière (1630–1633) and the later and more formal Principia philosophiae (1644), Descartes put forward a genuine natural philosophy, as opposed to the kind of mixed mathematical investigations found in his Dioptrics or his mechanical writings. (See the treatment of those domains in “Descartes: Mathematics and Physics” in DSB vol. 4.) Central to this natural philosophy is a conception of a world created and sustained by God and governed by laws of nature. Indeed, Descartes was arguably the first to make the idea of a law of nature central to his conception of physics. This view, in turn, grounded a program for explaining the present state of the world by showing how it could be derived from an initial state, evolving in accordance with those laws of nature. In these respects, among others, Descartes’s program offers an interesting contrast to the very influential view of nature found in contemporaries such as Galileo.

There was a standard distinction between pure mathematics and mixed mathematics that dates far before the seventeenth century. Pure mathematics included geometry and arithmetic and was the pure study of mathematical objects such as geometrical objects and numbers. Mixed mathematics, however, included such domains as astronomy, optics, music, mechanics, and, by the seventeenth century, motion. Mixed mathematics was mathematical insofar as it treated its subjects with the tools of mathematics, but it differed from pure mathematics insofar as it applied to the physical world. It also differed from physics or natural philosophy, terms generally synonymous in the period. For an Aristotelian physicist, natural philosophy was limited to the natural world, the world of things with natures, such as the Aristotelian elements (fire, air, water, and earth), living things, and appropriate mixtures. This differs from the mixed mathematical science of mechanics, which treats machines, which are artificial and have no nature properly speaking. For Descartes and some of his contemporaries, though, the distinction between the natural and the artificial had been broken down, thus making this distinction between mixed mathematics and natural philosophy irrelevant. (See the treatment of this issue in “Descartes” in DSB vol. 4.) However, natural philosophy was also distinguished from the mixed mathematical sciences by virtue of the fact that in natural philosophy, one dealt with the true causes and explanations of things, and not just their mathematical descriptions at least in principle.

Descartes worked on both sides of the divide. His Dioptrics (1637) and essay on mechanics (Explication des engins par l’aide desquels on peut avec une petite force lever un fardeau fort pesant of 1637) can be read as essays in mixed mathematics, though even in these texts Descartes shows his interest in understanding the true cause of the phenomena. But in Le monde (1630–1633) and more especially in the Principia philosophiae (1644) his goal was a complete natural philosophy, beginning with first principles and deriving a complete account of the world from them.

At the bottom level are the first principles, what he called his first philosophy or his metaphysics. These included the existence and nature of the soul or mind (the first thing we come upon when we philosophize in order), followed by God, and finally the existence and nature of matter or body. These are treated in part I and the beginning of part II of the Principia philosophiae, though they are treated at greater length in the Meditations (1641). (These were discussed less systematically in Le monde, though they did enter into the details of the arguments.) Whereas the soul would enter into his account of the human being, it is God and the nature of body that were most at issue in his account of the physical world.

Descartes argued that the nature of body was to be extended. For him that meant that in the strictest sense bodies had geometrical properties and nothing else: Bodies were the objects of geometry made real, and nothing else. And so, apparent properties of bodies such as hot or cold, wet or dry (to take the Aristotelian primary qualities), or color, are just sensations in the mind, grounded in the size, shape and motion of the smaller parts that make up bodies. It also follows from this conception that bodies have no inherent tendency to move in any particular direction. The natural tendency fire has to rise or earth to fall must be explained, again, in terms of the size, shape and motion of the parts that make up the bodies in question, as they interact with the other bodies in their environment. Another consequence of this conception of body is that there is no empty space. Any volume constitutes an extension, and because one cannot have an extension without a substance in which it inheres, Descartes argued that any volume will be an extended substance and therefore a body. For that reason Descartes did not recognize space as something over and above body: To talk about space is just to talk about bodies in an abstract way. To say that a body D can occupy the same space that is now occupied by a body C is to say that it could happen that D hold the same relation to some other bodies A and B that C now bears to those bodies. And because all space is occupied, even though the universe as a whole is infinite, Descartes argued that all motion is ultimately circular, as bodies move out of the way of other bodies in order to make way for the other bodies to enter the spaces where they had formerly been.

Laws of Motion . Motion can be defined in terms of the relation of bodies to one another. However, to understand the laws of motion, Descartes turned to the general cause of motion, God. Whereas the laws of nature (laws of motion) are first introduced in chapter 7 of Le monde, the most systematic presentation was later in the Principia philosophiae. The discussion there began with a characterization of God as the “universal and primary cause [of motion], which is the general cause of all motions which are in the world” (Principia part II § 36). God’s activity in sustaining the world from moment to moment gives rise to an important general rule: “from the sole fact that God moved the parts of matter when he first created them, and now conserves matter as a whole in the same way and with the same order with which he first created it, it is most consistent with reason that we think that he always conserves the same amount of motion in it” (Principia part II § 36). This amount is what he called quantity of motion, the sum of the size times the speed of the particles that make up the universe. (Note here that this is not what later came to be called momentum. Directionality, what Descartes called determination is not governed by this law, only speed, a scalar quantity.)

Descartes did not identify this general conservation law as a law. It is a very general constraint that governs the universe as a whole, and did not say anything about the behavior of particular bodies. For that reason, in the following sections Descartes introduced three specific constraints, each of which was explicitly identified as a law of nature(lex naturae). The first law is that “each and every thing, insofar as it can [quantum in se est] perseveres in the same state, nor is it ever moved unless by an external cause.” More specifically, Descartes inferred from this that “what is once moved, always proceeds to move” (Principia part II § 37). This is a law of the persistence of motion in an individual body, understood as a special case of the persistence of any property bodies have. The second reads: “every motion in itself is straight and therefore that which moves circularly always tends to recede from the center of the circle which it describes” (Principia part II § 39). This is a law of the persistence of directionality in an individual body. These two laws are often regarded as Descartes’s law of inertia, connecting them to Newton’s first law of motion. But this is misleading. For Descartes and his contemporaries, inertia was the property bodies have by virtue of which they tend to come to rest. For Descartes these laws dealt with the property bodies have by virtue of which they remain in rectilinear motion. The third law governs the collision of bodies:

When a moving body comes upon another, if it has less force for proceeding in a straight line than the other has to resist it, then it is deflected in another direction, and retaining its motion, changes only its determination. But if it has more, then it moves the other body with it, and gives the other as much of its motion as it itself loses. (Principles, part II, § 40)

Unlike the conservation principle and the first two laws, all of which deal with the persistence of certain features of bodies, this law can be thought of as reconciling the behavior of two bodies whose motion and direction would tend to be conserved, but because of the impenetrability of bodies, cannot. Descartes followed this with seven rules of impact, showing how the third law can be applied to the case of direct collision under certain assumptions, such as that the bodies are perfectly hard and isolated from all other bodies. In the examples Descartes made it clear how collisions are meant to be governed by his general conservation principle, and how he thought the forces involved are to be calculated. Descartes’s collision rule turned out to be very problematic. It is not at all clear what exactly he meant by force in the law, and how bodies that contain only extension can have either a force for proceeding or a force of resistance. The rules of impact drew serious criticisms from a number of later people, most notably Christiaan Huygens and Gottfried W. von Leibniz, who showed that they are inconsistent with a relativistic conception of motion and with certain plausible wider constraints that one might want to impose on a scientific theory.

Even though the laws were somewhat suspicious, particularly the collision law and the rules of impact that are connected with it, the overall view of natural philosophy and the physical world were important and influential. What Descartes offered was a conception of a world governed by laws of nature, grounded in God. Even though Descartes himself did not present them in mathematical form, because they could in principle be given in terms of size, shape, and motion, it was a conception of a law-governed universe that was well-suited to a mathematical physics. Another important feature of the view was that the basic laws are understood in terms of the conservation of certain features of bodies. This conception of physics would characterize the conception of physics found later in Leibniz’s system.

Structure of the World . With these laws in place, Descartes then proceeded to account for the current state of the world in outline. He began with an hypothesis about the initial state of the world, an assumption of random sized initial bodies in chapter 6 of Le monde and of uniform sided initial bodies in Principia part III § 46. He then showed how from this initial state and the laws of nature, these initial bodies would divide themselves into bodies of three different sizes, which he called elements. Because the world is a plenum, and all motion circular, the universe will become divided into an infinity of vortices of fluid matter, each with a sun (or star) at the center which will be the source of light, understood as centrifugal pressure in the vortex. In Le monde(chapter 9) the larger masses of matter from the initial creation form planets and comets, the former staying within a single vortex and rotating around its sun, the latter migrating from one vortex to another, moving at the interstices between vortices. In part III of the Principia philosophiae, Descartes argued that these larger masses are formed from suns (stars) which become encrusted with sunspots, and are either captured by vortices (and become planets) or wander from one vortex to another (and become comets).

In part four of the Principia Descartes dealt with the structure of the Earth in some detail. Descartes argued that the Earth has three regions. Because it originated as a star, encrusted by sunspots, it still retains at its center the same celestial matter found in other stars. Above that is the dense and opaque material that derives from the sunspots that encrusted the original star. The top layer is a mixture of different elements, resulting from the interaction between the second layer and the particles in the vortex surrounding the Earth. All the bodies in human experience are made up of the parts of this third layer. Such terrestrial bodies are not heavy in themselves, but only because they are driven toward the center of the Earth by the heavenly matter that surrounds the Earth and forms a vortex around it. Descartes went on to deal with a wide variety of terrestrial phenomena, including the formation of mountains and valleys, the nature of the air, oceans and their tides, the properties of various chemicals and metals and why they are found where they are in the Earth, the properties of fire and how it is generated, and the properties of glass. The account of the bodies found on Earth ends with a lengthy account of the magnet, giving an ingenious mechanistic model that attempts to unify a wide variety of empirical data about the behavior of magnets by way of a few simple hypotheses.

The main body of the Principia ends with terrestrial physics. However, Descartes had intended to end with an account of living things, derived in the same way that he attempted to derive the properties of the Earth, arguing genetically from some initial assumptions and the laws of nature, in a broadly evolutionary fashion. Descartes was working on these issues in his last years, though never fully integrated his account of the life sciences into his natural philosophy. (See the treatment of Descartes’s work in the life sciences in “Descartes: Physiology” in DSB vol. 4.)

Contrast with Galileo . Though often paired with Galileo as one of the founding fathers of the New Science of the seventeenth century, Descartes actually saw himself as doing something radically different. In a letter to Marin Mersenne from 11 October 1638, Descartes conveyed his comments on Galileo’s program, with particular reference to the Discorsi (1637). He wrote:

I find in general that he philosophizes much better than is common, insofar as he avoids as much as he can the errors of the schools, and tries to examine physical matters using mathematical reasons. In that I am entirely in agreement with him.… But it seems to me that he is greatly lacking insofar as he continually makes digressions and never stops to explain a matter in its entirety. This shows that he hasent examined them in arder, and without having considered the first causes of nature, he has only looked for the reasons for certain particular effects, and thus that he has built without a foundation.

This nicely captures the spirit of the natural philosophical approach that Descartes took in contrast to the mixed mathematical approach that he saw in Galileo. For Descartes, what was important was bringing the explanation of phenomena back to their ultimate causes, building a science grounded in first principles. When possible, he was happy to derive mathematically rigorous representations of nature, like Galileo, as he did, for example, with the sine law of refraction. (See the treatment of refraction in “Descartes: Mathematics and Physics” in the original DSB). But for Descartes, the mathematical expressions were empty unless accompanied by an account of the true causes.



Regulae ad directionem ingenii. Edited by Giovanni Crapulli. Gravenhage, Netherlands: Martinus Nijhoff, 1966. This is a scholarly edition of the text.

Régles utiles et claires pour la direction de l’esprit en la recherche de la vérité. Edited and translated by Jean-Luc Marion and Pierre Costabel. The Hague: Martinus Nijhoff, 1977. This is a translation of the Regulae with an extensive commentary on the scientific themes.

Ecrits physiologiques et médicaux. Edited by Vincent Aucante. Paris: Presses Universitaires de France, 2000.

Tutte le lettere 1619–1650. Edited by Giulia Belgioioso et al. Milan: Bompiani, 2005. This is a new edition of all Descartes’s correspondence, in original language with Italian translation and excellent notes on the scientific and mathematical letters.


Aiton, Eric J. The Vortex Theory of Planetary Motions. London: Macdonald, 1972.

Ariew, Roger. Descartes and the Last Scholastics. Ithaca, NY: Cornell University Press, 1999.

Armogathe, Jean Robert, and Giulia Belgioioso. Descartes, Principia Philosophiae: 1644–1994: Atti del convegno per il 350o anniversario della pubblicazione dell’opera. Naples, Italy: Vivarium, 1996. This is a major collection of writings on Descartes’s scientific work from a conference given on the anniversary of the publication of the Principia.

———, and Vincent Carraud. Bibliographie Cartésienne : 1960–1996. Lecce, Italy: Conte Editore, 2003.

Aucante, Vincent. La philosophie médicale de Descartes. Paris: Presses Universitaires de France, 2006.

Belgioioso, Giulia, ed., et al. Descartes, Il Metodo e I Saggi : Atti del convegno per il 350o anniversario della pubblicazione del Discours de la méthode e degli Essais. Rome: Istituto della enciclopedia italiana, 1990. This is a major collection of writings on Descartes’s scientific work from a conference given on the anniversary of the publication of the Discourse and Essays.

Clarke, Desmond M. Descartes: A Biography. Cambridge, U.K.: Cambridge University Press, 2006.

Des Chene, Dennis. Physiologia: Natural Philosophy in Late Aristotelian and Cartesian Thought. Ithaca, NY: Cornell University Press, 1996.

———. Spirits and Clocks: Machine and Organism in Descartes. Ithaca, NY: Cornell University Press, 2001.

Duchesneau, François. Les modèles du vivant de Descartes à Leibniz. Paris: J. Vrin, 1998.

Garber, Daniel. Descartes’ Metaphysical Physics, Science and Its Conceptual Foundations. Chicago: University of Chicago Press, 1992.

Gaukroger, Stephen. Descartes: Philosophy, Mathematics and Physics. Sussex and Totowa, N.J.: Harvester Press and Barnes and Noble Books, 1980. This is an important collection that contains a number of essays that have become classics, including essays by John Schuster, Michael Mahoney, Martial Gueroult, and Alan Gabbey.

———. Descartes: An Intellectual Biography. Oxford: Oxford University Press, 1995.

———, John Schuster, and John Sutton. Descartes’ Natural Philosophy, Routledge Studies in Seventeenth-Century Philosophy. London: Routledge, 2000. This is a large collection of late twentieth century studies focused on Descartes’s science.

———. Descartes’ System of Natural Philosophy. Cambridge, U.K.: Cambridge University Press, 2002.

Daniel Garber

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René Descartes

René Descartes

The French thinker René Descartes (1596-1650) is called the father of modern philosophy. He initiated the movement generally termed rationalism, and his Discourse on Method and Meditations defined the basic problems of philosophy for at least a century.

To appreciate the novelty of the thought of René Descartes, one must understand what modern philosophy, or rationalism, means in contrast to medieval, or scholastic, philosophy. The great European thinkers of the 9th to 14th century were not incapable of logical reasoning, but they differed in philosophic interests and aims from the rationalists. Just as the moderns, from Descartes on, usually identified philosophy with the natural and pure sciences, so the medievals made little distinction between philosophical and theological concerns.

The medieval doctors, like St. Thomas Aquinas, wanted to demonstrate that the revelations of faith and the dictates of reason were not incompatible. Their universe was that outlined by Aristotle in his Physics—a universe in which everything was ordered and classified according to the end that it served. During the Renaissance, however, men began exploring scientific alternatives to Aristotle's hierarchical universe. Further, new instruments, especially Galileo's telescope, added precision to scientific generalizations.

By the beginning of the 17th century the medieval tradition had lost its creative impetus. But the schoolmen, so called because they dominated the European universities, continued to adhere dogmatically to the traditional philosophy because of its association with Catholic theology. The rationalists, however, persistently refused professorships in order to preserve their intellectual integrity or to avoid persecution. They rejected the medieval practice of composing commentaries on standard works in favor of writing original, usually anonymous, treatises on topics suggested by their own scientific or speculative interests. Thus the contrast is between a moribund tradition of professorial disputes over trivialities and a new philosophy inspired by original, scientific research.

Descartes participated in this conflict between the scholastic and rationalist approaches. He spent a great part of his intellectual effort—even to the extent of suppressing some of his writings—attempting to convince ecclesiastical authorities of the compatibility of the new science with theology and of its superiority as a foundation for philosophy.

Early Life

Descartes was born on March 31, 1596, in La Haye, in the Touraine region, between the cities of Tours and Poitiers. His father, Joachim, a member of the minor nobility, served in the Parliament of Brittany. Jeanne Brochard Descartes, his mother, died in May 1597. Although his father remarried, Descartes and his older brother and sister were raised by their maternal grandmother and by a nurse for whom he retained a deep affection.

In 1606 Descartes entered La Flèche, a Jesuit college established by the king for the instruction of the young nobility. In the Discourse Descartes tells of the 8-year course of studies at La Flèche, which he considered "one of the most celebrated schools in Europe." According to his account, which is one of the best contemporary descriptions of 17th-century education, his studies left him feeling embarrassed at the extent of his own ignorance.

The young Descartes came to feel that languages, literature, and history relate only fables which incline man to imaginative exaggerations. Poetry and eloquence persuade man, but they do not tell the truth. Mathematics does grasp the truth, but the certainty and evidence of its reasoning seemed to Descartes to have only practical applications. Upon examination, the revelations of religion and morals seem as mysterious to the learned as to the ignorant. Philosophy had been studied by the best minds throughout the centuries, and yet "no single thing is to be found in it which is not subject to dispute." Descartes says that he came to suspect that even science, which depends upon philosophy for its principles, "could have built nothing solid on foundations so far from firm."

Travel and First Writings

The 18-year-old Descartes left college with a reputation for extreme brilliance. In the next years he rounded out the education befitting a young noble. He learned fencing, horsemanship, and dancing and took a law degree from Poitiers.

From 1618 to 1628 Descartes traveled extensively throughout Europe while attached to various military units. Although a devout Catholic, he served in the army of the Protestant prince Maurice of Nassau but later enlisted in the Catholic army of Maximilian I of Bavaria. Living on income from inherited properties, Descartes served without pay and seems to have seen little action; he was present, however, at the Battle of Prague, one of the major engagements of the Thirty Years War. Descartes was reticent about this period of his life, saying only that he left the study of letters in order to travel in "the great book of the world."

This period of travel was not without intellectual effort. Descartes sought out eminent mathematicians, scientists, and philosophers wherever he traveled. The most significant of these friendships was with Isaac Beeckman, the Dutch mathematician, at whose suggestion Descartes began writing scientific treatises on mathematics and music. He perfected a means of describing geometrical figures in algebraic formulas, a process that served as the foundation for his invention of analytic geometry. He became increasingly impressed with the extent to which material reality could be understood mathematically.

During this period Descartes was profoundly influenced by three dreams which he had on Nov. 10, 1619, in Ulm, Germany. He interpreted their symbols as a divine sign that all science is one and that its mastery is universal wisdom. This notion of the unity of all science was a revolutionary concept which contradicted the Aristotelian notion that the sciences were distinguished by their different objects of study. Descartes did not deny the multiplicity of objects, but rather he emphasized that only one mind could know all these diverse things. He felt that if one could generalize man's correct method of knowing, then one would be able to know everything. Descartes devoted the majority of his effort and work to proving that he had, in fact, discovered this correct method of reasoning.

From 1626 to 1629 Descartes resided mainly in Paris. He acquired a wide and notable set of friends but soon felt that the pressures of social life kept him from his work. He then moved to Holland, where he lived, primarily near Amsterdam, for the next 20 years. Descartes cherished the solitude of his life in Holland, and he described himself to a friend as awakening happily after 10 hours of sleep with the memory of charming dreams. He said his life in Holland was peaceful because he was "the only man not engaged in merchandise." There Descartes studied and wrote. He carried on an enormous correspondence throughout Europe, and in Holland he acquired a small, but dedicated, set of friends and disciples. Although he never married, Descartes fathered a natural daughter who was baptized Francine. She died in 1640, when she was 5.

First Works

Descartes's research in mathematics and physics led him to see the need for a new methodology, or way of thinking. His first major work, Rules for the Direction of the Mind, was written by 1629. Although circulated widely in manuscript form, this incomplete treatise was not published until 1701. The work begins with the assumption that man's knowledge has been limited by the erroneous belief that science is determined by the various objects of experience. The first rule therefore states that all true judgment depends on reason alone for its validity. For example, the truths of mathematics are valid independently of observation and experiment. Thus the second rule argues that the standard for any true knowledge should be the certitude demanded of demonstrations in arithmetic and geometry. The third rule begins to specify what this standard of true knowledge entails. The mind should be directed not by tradition, authority, or the history of the problem, but only by what can clearly be observed and deduced.

There are only two mental operations that are permissible in the pure use of reason. The first is intuition, which Descartes defines as "the undoubting conception of an unclouded and attentive mind"; the second is deduction, which consists of "all necessary inference from other facts that are known with certainty. "The basic assumption underlying these definitions is that all first principles are known by way of self-evident intuitions and that the conclusions of this "seeing into" are derived by deduction. The clarity and distinctness of ideas are for Descartes the conceptual counterpart of human vision. (For example, man can know the geometry of a square just as distinctly as he can see a square table in front of him.)

Many philosophers recognized the ideal character of mathematical reasoning, but no one before Descartes had abstracted the conditions of such thinking and applied it generally to all knowledge. If all science is unified by man's reason and if the proper functioning of the mind is identified with mathematical thinking, then the problem of knowledge is reduced to a question of methodology. The end of knowledge is true judgment, but true judgment is equivalent to mathematical demonstrations that are based on intuition and deduction. Thus the method for finding truth in all matters is merely to restrict oneself to these two operations.

According to the fourth rule, "By method I mean certain and simple rules, such that if a man observe them accurately, he shall never assume what is false as true … but will always gradually increase his knowledge and so arrive at a true understanding of all that does not surpass his powers." The remaining sixteen rules are devoted to the elaboration of these principles or to showing their application to mathematical problems. In Descartes's later works he refines these methodological principles, and in the Meditations he attempts a metaphysical justification of this type of reasoning.

By 1634 Descartes had written his speculative physics in a work entitled The World. Unfortunately, only fragments survive because he suppressed the book when he heard that Galileo's Dialogue on the Two Great Systems of the Universe had been condemned by the Catholic Church because of its advocacy of Copernican rather than Ptolemaic astronomy. Descartes also espoused the Copernican theory that the earth is not the center of the universe but revolves about the sun. His fear of censure, however, led him to withdraw his work. In 1634 he also wrote the brief Treatise on Man, which attempted to explain human physiology on mechanistic principles.

Discourse and Meditations

In 1637 Descartes finished Discourse on Method, which was published together with three minor works on geometry, dioptrics, and meteors. This work is significant for several reasons. It is written in French and directed to men of good sense rather than professional philosophers. It is autobiographical and begins with a personal account of his education as an example of the need for a new method of conducting inquiry.

The work contains Descartes's vision of a unity of science based on a common methodology, and it shows that this method can be applied to general philosophic questions. In brief, the method is a sophistication of the earlier Rules for the Direction of the Mind. In the Discourse Descartes presents four general rules for reducing any problem to its fundamentals by analysis and then constructing solutions by general synthesis.

Meditations on First Philosophy appeared in 1641-1642 together with six (later seven) sets of objections by distinguished thinkers including Thomas Hobbes, Antoine Arnauld, and Pierre Gassendi and the author's replies. The Meditations is Descartes's major work and is one of the seminal books in the history of philosophy. While his former works were concerned with elaborating a methodology, this work represents the systematic application of those rules to the principal problems of philosophy: the refutation of skepticism, the existence of the human soul, the nature of God, the metaphysical basis of truth, the extent of man's knowledge of the external world, and the relation between body and soul.

The first meditation is an exercise in methodological skepticism. Descartes states that doubt is a positive means of ascertaining whether there is any certain foundation for knowledge. All knowledge originates either from the senses or from the mind. Examples of color blindness, objects seen in perspective, and so on testify to the distortions inherent in vague sense perception. The recognition of these phenomena as distorted suggests a class of clear perceptions which are more difficult to doubt. But Descartes then points out that such images appear as clear to man in dreams as in an awakened state. Therefore all sensory experience is doubtful because sense data in itself does not indicate whether an object is seen or imagined, true or false.

What about the realm of pure ideas? Descartes simplifies the argument by asking whether it is possible to doubt the fundamental propositions of arithmetic and geometry. Man cannot doubt that two plus two equals four, but he may suspect that this statement has no reality apart from his mind. The standard of truth is the self-evidence of clear and distinct ideas, but the question remains of the correspondence of such ideas to reality. Descartes imagines the existence of an all-powerful "evil genius" who deceives man as to the content of his ideas, so that in reality two plus two equals five.

The second meditation resolves these skeptical issues in a deceptively simple manner by arguing that even if it is doubtful whether sense images or ideas have objects, it is absolutely true that man's mind exists. The famous formula "I think, therefore, I am" is true even if everything else is false. Descartes's solution is known as subjectivism, and it is a radical reversal of previous theories of knowledge. Whereas nature had been assumed to be the cause of man's images and ideas, Descartes states that man is a "thinking thing" whose subjective images and ideas are the sole evidence for the existence of a world.

The third meditation demonstrates that God is "no deceiver," and hence clear and distinct ideas must have objects that exactly and actually correspond to them. Descartes argues that the idea of God is an effect. But an effect gets its reality from its cause, and a cause can only produce what it possesses. Hence either Descartes is a perfect being or God exists as the cause of the idea of God.

The fourth meditation deals with the problem of human error; insofar as man restricts himself to clear and distinct ideas, he will never err. With this connection between ideas and objects Descartes can emerge from his doubts about knowledge. The external world can be known with absolute certainty insofar as it is reducible to clear and distinct ideas. Thus the fifth meditation shows the application of methodology to material reality in its quantifiable dimensions, that is, to the extent to which material reality can be "the object of pure mathematics."

The sixth, and final, meditation attempts to explain the relation between the human soul and the body. Since Descartes believed in mechanism, there could be no absolute connection between a free soul and a bodily machine. After considerable hesitation he expresses the relation between mind and matter as a "felt union." The body is the active faculty that produces the passive images and imaginings man finds in his mind. Actually Descartes's explanation is logically impossible in terms of the "subjective" separation of mind; similarly, the unresolved dualism of the "felt union" violates the principle of assenting only to clear and distinct ideas.

The remainder of Descartes's career was spent in defending his controversial positions. In 1644 he published the Principles of Philosophy, which breaks down the arguments of the Meditations into propositional form and presents extra arguments dealing with their scientific application. In 1649 Descartes accepted an invitation from Queen Christina of Sweden to become her teacher. There he wrote The Passions of the Soul, which is a defense of the mind-body dualism and a mechanistic explanation of the passions. But Descartes's health was undermined by the severity of the northern climate, and after a brief illness he died in Stockholm in 1650.

Further Reading

The most complete edition of Descartes's works in English is The Philosophical Works of Descartes, translated by Elizabeth S. Haldane and G.T.R. Ross (2 vols., 1955), although many editions of individual works in new translations are available in paperback. The standard biography is Haldane's Descartes: His Life and Times (1905; repr. 1966). The best general introductions to Descartes's philosophy are A. Boyce Gibson, The Philosophy of Descartes (1932); Stanley V. Keeling, Descartes (1934; 2d ed. 1968); and Albert G. A. Balz, Descartes and the Modern Mind (1952). Works on specialized topics of an analytic or critical nature include Norman Kemp Smith, Studies in the Cartesian Philosophy (1902) and New Studies in the Philosophy of Descartes: Descartes as Pioneer (1952); Jacques Maritain, Three Reformers: Luther Descartes, Rousseau (trans. 1928) and The Dream of Descartes (trans. 1944); and Leslie J. Beck, The Method of Descartes: A Study of the Regulae (1952). □

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Descartes, René

Descartes, René



René Descartes (1596–1650) was born at La Haye, in Touraine, near Poitou, into a family of merchants and lower civil servants aspiring to the petite noblesse. A second son, he was put to school with the Jesuits at the newly founded Collège Royale of La Flèche where, until he was sixteen, he studied, first, the trivium, then “philosophy”—that is, logic, physics, and metaphysics. Later in the curriculum, “morality” was added to logic and mathematics to physics; in mathematics his talent was at once evident. Two aspects of his education are notable: he received a thoroughly “modern” intellectual training, in which bodily fitness was valued, and Galileo’s physics was early and naturally absorbed into Jesuit teaching.

Between 1612, when he left school, and 1618, when he took up the profession of arms, the events of Descartes’s life are unclear. He was for a time in Paris and may then have come into contact with the scientific group around the Minim Father, Marin Mersenne, at the Place Royale. After some hesitation he evidently decided on a military career. As a soldier of fortune he took part in the Thirty Years’ War, fighting with the Dutch, who in spite of their Protestantism allied with France against the Hapsburgs. During the night of November 10, 1619, Descartes had his famous dream of a universal and unified science; in his German poele (”stoveheated room”) that winter he worked out his “rules for thinking,” finally published in 1637 as the Discourse on Method.

From 1620 until his death, Descartes led a life with neither a fixed profession nor a fixed abode. He was, simply, a thinker; his inherited income, his books, and his occasional patrons sufficed for his needs. He traveled through Europe, including Italy, before 1628, making Paris (and in Paris, Mersenne) his center; thereafter, until 1649, he lived chiefly in Holland, the first of a stream of immigrant visitors to profit from the freedom and stimulus of that country.

Descartes’s fellowship was varied—the scientist Isaac Beeckman in Breda, who like him was deeply concerned with establishing a method for the new sciences; Claudius Salmasius, a French theologian at Leiden; the mathematicians Hortensius at Amsterdam and Golius and Van Schooten at Leiden; among doctors, the anatomist Plempius, with whom he studied; Plempius’ disciples Heereboord and Heydanus, responsible for the introduction of “Cartesianism” into the academies; Étienne de Courcelles, who translated the Discourse into Latin; the polymath Constantijn Huygens, secretary to the prince of Orange (Descartes played a part in the education of his scientific son, Christiaan Huygens). His correspondence was enormous, and he maintained his connections with French scientists. He lived in Deventer, Leiden, Egmond, and Amsterdam, making several trips to France; in 1649 in the service of Queen Christina, he accepted an appointment to Stockholm, where he died in 1650.

Descartes’s published work shows great consistency and care. In 1629 he was busy with a treatise in metaphysics, later expanded and published as the Meditations in 1641. From 1629 to 1633 he worked on his cosmological study, Le monde (1664), a book in two sections, one ostensibly on light (or action at a distance), the other on man; but, as he frankly reported in the Discourse of 1637, he was alarmed by the condemnation of Galileo’s theories and did not publish the work (it was posthumously published in 1662 and 1664). At this point he evidently turned back to his dream and contemplations on method; in 1637 his vernacular Discourse appeared, written for ordinary thinking people, followed by long essays exemplifying its application to optics, meteorology, and geometry. Perhaps because of his nervousness over his discontinued cosmological speculation, Descartes made special efforts to secure approval for his book, sending a copy to the Jesuit Pére Noel, rector of La Fléche, and seeking approval of the book, through Mersenne, from the French chancellor Pierre Séguier.

The Discourse was influential in many areas, from literary explication de texte to metaphysics. Appropriately, in a work in which human certainty is reduced to man’s consciousness of his own thinking processes, Descartes described the etiology of the treatise itself—what sort of an instrument he himself was, how he was trained, where and under what conditions he got his idea of universal method, how he tested his method, how he came to write it. Throughout Descartes’s work there are patches of autobiography, presented not as self-indulgence but as data relevant to the substance presented. Although the Discourse records his approval of his own training, it nonetheless, with its appendages, revised (or reformed) the Jesuits’ philosophical curriculum, as it did the teaching of other groups. Logic, physics, and metaphysics all suffered reorganization at Descartes’s hands, as did mathematics and morality (the last subject more fully developed with the appearance of Les passions de lame in 1649). In 1641 his Meditations came out, expansions both of the Discourse and his early metaphysical speculations and, in 1644, his Principia philosophiae. Though he was soon embroiled in methodological and theological polemic, particularly with Dutch Reformed divines, his social success was enhanced by a philosophical friendship with the bluestocking Princess Elizabeth, daughter of the dispossessed elector palatine, as well as by the patronage of Queen Christina.

Descartes made substantial contributions to mathematics, physics, and psychology. In his own terms, his work in geometry and optics has remained viable: Cartesian geometry is still a legitimate entry to that discipline; his description of the operation of the eye, though since greatly refined, is the “correct” one. His “method,” important for its influence in the social as well as in the natural sciences, has the following simple rules: (1) to accept nothing as true not clearly recognizable as such; (2) to divide up each difficulty into as many parts as possible; (3) to carry on reflections in due order, from the simplest part to the most complex combination; and (4) to make regular enumerations and reviews, in order to be certain of having made no omissions.

These regulations, striking for their common sense, involve two major presuppositions: the first, that ideas, fixed and reliable as numbers and mathematical ratios, build and follow as inexorably and securely upon one another as do mathematical processes; the second, that the proposition cogito, ergo sum (”I think, therefore I am”) is radically true. Another way of stating the first is that Descartes believed in the truth of mathematics, and therefore used it as a model for his thinking about thinking, or that he was a thorough rationalist. Another way of stating the second is that Descartes used skepticism to establish an ontology based— again, in sharp break with the philosophical tradition—upon the self’s irreducible recognition of the thinking self. From that conviction and by means of his own method, he constructed his (remarkably arrogant) ontological proof of God and his definitions of the existence of the material world and the laws of its nature.

Accompanying the crucial importance he attributed to mind is his notion of its separation from body, or matter; the sharp distinction he drew between mind and body resulted in part from his attempt to relate Galileo’s mechanist physics—for him, in spite of the ban unassailably true—to the immaterial process of rationality and, through that process, to the immaterial deity in whose existence he believed. One result of that radical separation of mind and matter is his extremely abstract conception of deity (justifiably criticized as deist rather than Christian); another is his mechanist psychology. Animals, indeed, he concluded to be machines: man, endowed with soul and mind, is thereby no mere mechanism. Les passions de I’âme deals with psychological manifestations as functionally as possible, translating inward “passion” into outward “action” and discussing the sensible appearances of behavior rather than the invisibilia of man’s inner life. Insofar as he could, relying heavily upon Harvey’s work and his own anatomical experience, Descartes provided a physiological explanation of behavior, one example of which (unfairly ridiculed) is his location of the soul in the pineal gland. Behavior was discussed in the “causal” terms of external stimuli and the passions classified as predictable reactions to certain situations and stimuli (e.g., wonder, desire, remorse, love and hatred, pride and shame). He was interested in such physiological manifestations of the passions as tears and flight. Psychology thus became a branch of “physics,” or physiology, a hypothesis with great influence upon subsequent psychological experimentation. The Cartesian beast-machine became the model for animal study in the eighteenth century; inevitably, in spite of Descartes’s precautions against such a step, La Mettrie presented the argument, firmly based in the Cartesian psychology, that man too is simply machine. In his effort to free thought and thinking from the debilitating influence of the mutable body and to exempt it, theoretically at least, from skewing by the passions, Descartes split inward life into two quite different and unrelated components, the rational and the emotional.

Rosalie L. Colie

[Other relevant material may be found inReasoning and logic; Thinking; Vision; and in the biographies ofDurkheimandKant.]


(1637) 1954 Discourse on Method. Translated with an introduction by Laurence J. Lafleur. New York; Liberal Arts Press. → First published as Discours de la méthode. … A paperback edition was published in 1960 by Penguin.

(1641) 1961 Meditations on First Philosophy. 2d ed., rev.New York: Bobbs-Merrill. → First published as Meditationes de prima philosophia, …

1644 Renati Des Cartes principia philosophiae. Amsterdam: Elsevier.

1649 Les passions de I’âme. Paris: Legras.

1664 Le monde de M. Descartes: Ou la traité de la lumiére et des autres principaux objects des sens; Avec un discours de I’action des corps et un autre des fièvres, composez selon les principes du même auteur. Paris: Bobin & Le Gras. → Published posthumously.

Oeuvres de Descartes. 12 vols. and index. Edited by Charles Adam and Paul Tannery. Paris: Cerf, 1897–1913.


Adam, Charles 1937 Descartes: Sa vie et son oeuvre. Paris: Boivin.

Baillet, Adrien (1691) 1946 La vie de Monsieur Descartes. Paris: Table Ronde.

Balz, Albert G. A. 1951 Cartesian Studies. New York: Columbia Univ. Press.

Brunschvicg, LÉon 1944 Descartes et Pascal: Lecteurs de Montaigne. New York and Paris: Brentano.

Cresson, AndrÉ 1962 Descartes: Sa vie, son oeuvre. Paris: Presses Universitaires de France.

Descartes et le cartésianisme hollandais. Edited by E. J. Dijksterhuis et al. 1950 Paris; Presses Universetaires de France.

Gilson, Étienne 1930 Études sur le rôle de la pensée médiévale dans la formation du système cartésien. Paris: Vrin.

Jaspers, Karl (1937) 1956 Descartes und die Philosophic. 3d ed. Berlin: de Gruyter.

KoyrÉ, Alexandre 1922 Essai sur l’idée de Dieu et les preuvres de son existence chez Descartes. Paris: Leroux.

Maritain, Jacques 1944 The Dream of Descartes. New York: Philosophical Library.

Paris, BibliothÉque Nationale 1937 Descartes: Notices bibliographiques et iconographiques. Edited by Thérèse d’Alverny. Paris: Bibliothèque Nationale.

Scott, J. F. 1952 The Scientific Work of René Descartes. London: Taylor & Francis.

Sebba, G. 1964 Bibliographia Cartesiana: A Critical Guide to the Descartes Literature, 1800–1960. The Hague: Nijhoff.

Serrurier, Cornelia (1943) 1951 Descartes: L’homme et le penseur. Paris: Presses Universitaires de France.

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Descartes, René

Descartes, RenÉ

René Descartes's philosophical importance for the advent of the modern scientific age is matched only by the difficulty of fully evaluating what his doctrines imply for religion. Born in Poitou, France, in 1596, Descartes lived most of his adult life in Holland, incurring the opposition, but also gaining the support, of Catholics and Protestants alike. He died in 1650 in Stockholm, where Queen Christina of Sweden had invited him to reside and instruct her in philosophy.

In his lifetime, he published works in both French and Latin, aimed at two slightly different audiences: Discourse on the Method of Rightly Conducting Reason and Reaching the Truth in the Sciences (French, 1637), Meditations on First Philosophy (Latin, 1641), Principles of Philosophy (Latin, 1644), and Passions of the Soul (French, 1649). Descartes also left unfinished works, notably Rules for the Direction of the Mind (Latin), The Search for Truth (Latin), The Universe or Treatise on Light (French), and Treatise on Man (French), as well as a voluminous correspondence in both French and Latin.

Method and faith

As a boy, Descartes attended the Jesuit College of La Flèche. Recalling his education in Discourse on the Method, Descartes denounces bookish learning and the vain pretense of scholastic philosophy, but favorably cites his love of poetry, his delight in mathematics, and his reverence for "our" theology. He emphasizes being firmly taught that revealed truths are above human intelligence. Stating moreover that the truths of faith have "always been first" in his beliefs, he explicitly says that these truths must be "set apart" from human opinions and must not be subjected to his method of universal doubt. Descartes consistently maintains this position throughout his work, from the early and unpublished Rules for the Direction of the Mind to the mature Principles of Philosophy, where article seventy-six gives divine authority unambiguous precedence over human reason. Youthful diaries dating from his years of wandering and soldiering (16181620) reveal a feverish, unconventional, religious imagination, coupled with devout impulses.

A critical aspect of Descartes's mature philosophy for issues of science and religion is that his theory of mind (res cogitans ) explicitly privileges free will over cognition. During an extended stay in Paris from 1620 to 1627, Descartes had frequent exchanges with leading religious figures: Marin Mersenne (15881648), who was also educated at La Flèche; Guillaume Gibieuf, a priest of the Oratory busy writing a book on freedom of the will; and Cardinal Pierre de Bérulle, who encouraged Descartes to pursue his reform of philosophy as a duty and vocation. In Rules for the Direction of the Mind, composed in the immediate wake of these meetings, Descartes affirms that revealed truths are held with even greater certainly than natural truths since "faith rests, not on an act of intelligence, but an act of will." He also distinguishes between cognition as such and the faculty of "affirming and denying" in an attempt to explain error, but the second faculty is not yet clearly identified with the free will, as it will be in the Meditations (1641) and in article thirty-two of the Principles of Philosophy (1644).

In 1628, Descartes moved to Holland in search of solitude. A letter to Mersenne dated April 15, 1630, reveals the extent to which physics and metaphysics were indivisibly combined in this search. Descartes explains that he would not have discovered the foundations of physics if he had not started with the rational discovery of self and God, which is indeed everyone's "first duty." God, Descartes maintains further, is "the first and most eternal" truth from which "all other truths proceed." Most dramatically, Descartes affirms that eternal truths are created: God has freely decreed that two and two make four, so that mathematical truths "depend on God's will no less than creatures." By 1630, while solving problems of mechanics and conducting dissections in his home, Descartes thus conceptualized divine freedom, the new physics, human self-knowledge, and dependence on God as intricately connected.

Cartesian naturalism

When Descartes learned of Galileo's condemnation in 1633, he cancelled plans to publish the cosmological Universe or Treatise on Light designed to unveil his new philosophy, citing at a later date "those whose authority has hardly less power over my action than my own reason over my thoughts." Instead, he published the Discourse on the Method anonymously in Leiden in 1637, along with "samples" of what his new method could achieve in geometry, optics and meteorology. Presenting his proof of self and God as pivotal to his own intellectual awakening, Descartes launches a framework in which physical phenomena, including biological phenomena, can be investigated experimentally according to materialist principles, while special mental events exhibiting voluntary features and characteristic of human beings are set apart and assigned to a distinct immaterial principle. In the Discourse, Descartes proceeds naturalistically in so far as he cites the empirical evidence of languages to conclude that the human "rational soul" is "in no way drawn from the potentiality of matter" and is therefore "not liable" to die with the body.

Cogito and freedom

Objections from all sides greeted Descartes's radical move to explain biological phenomena by means of inert microcorpuscular processes, as well as Descartes's bold noetic proof of self ("I think, therefore I am") and God. In 1639, desirous to clarify his views and to answer his critics, Descartes began writing his masterpiece, Meditations on First Philosophy, published in Paris in 1641. Composed in Latin, the text of the Meditations is followed by objections and answers, and is dedicated to Paris theologians. This time, the reader is led through a six-day journey of introspection and analysis designed to purge the mind of naïve empiricism, secure new grounds of noetic truth by rooting the human soul in God, and promote scientific investigation of the material universe (res extensa ) as a way to cultivate personal happiness while working for the common good. From the demonic ordeal of the first day to the orderly reintegration of soul and body on the last, Descartes's core concern is to champion the inalienable gift of freedom that marks human beings as created in God's image. God, Descartes explains, has "left it in my power not to err" since he is always free to suspend judgment when evidence is insufficient. No evil demon, however powerful, can compel him to affirm as true what is merely doubtful. Human freedom thus manifests the will's inherent predilection for what is good and true, even in the absence of any known good or truth. Moreover, clarification in Meditation VI that the senses are meant for immediate survival and must therefore not usurp the function of reason in proposing to our freedom truths to be affirmed allows the same responsible exercise of judgment afforded by geometry to extend to the physical and experimental sciences.

The moral value of the scientific project thus lies primarily in the special opportunity it provides for deliberately searching out and affirming the truths that God has freely decreed. Significantly, in the Principles of Philosophy, charmingly dedicated to his favorite pupil Elizabeth of Bohemia, the principle of human freedom (article six) precedes the principle of cognitive certainty or cogito (article seven): The freedom to abstain from error is even more fundamental than the first cognitive certainty I think; I am. And as article thirty-seven goes on to explain, a human being's principle perfection lies in having a free will, and people act worthily whenever they deliberately choose what is true.

Further development of Descartes's views relating to proper use of the free will, truth, and human happiness, is found in Descartes's numerous letters to Elizabeth, and in the treatise on The Passions of the Soul, published in 1649. Descartes distinguishes between autonomous acts of will that terminate in bodily actions and those that terminate "in the soul itself, as for example, when we resolve to love God, or more generally, apply our thought to some immaterial object." Acts of the will that are based on false opinions leave one vulnerable to regret and remorse, while those that are securely based on knowledge of the truth lead instead to happiness and inner serenity. Descartes's letter to Queen Christina dated November 20, 1647, may serve to summarize Descartes's integration of religion and science since he declares that the highest good, for each and every human being, consists in "a firm will to do what is good and in the serenity to which this leads."


Although what is crudely described as Cartesian dualism has been mostly rejected by later philosophy, the problem of human freedom raised by Descartes and explained by him on the basis of a distinct, substantial, and immaterial spiritual principle (res cogitans ), has be no means disappeared. The linguist Noam Chomsky has repeatedly drawn attention to some of the advantages of Cartesian rationalism for the defense of universal human dignity. In France, the philosopher Nicolas Grimaldi continues to emphasize the relevance of Cartesian freedom, while Jean-Luc Marion has in turn used Descartes as a springboard to elaborate new perspective on ethics. Most importantly, Cartesian scholars continue to discover seminal ideas in Descartes regarding the spiritual dimension of science. Daniel Garber, in particular, has shed light on the distinctive metaphysical features of Cartesian physics; Gary Hatfield has called attention to the deeply religious character of Descartes's notion of force; and Matthew Jones has initiated new questions on the spiritual dimension of Descartes's mathematics.

See also Cartesianism; Freedom; Modernity


chomsky, noam. language and thought. wakefield, r.i.: moyer bell, 1993.

cottingham, john, ed. descartes. oxford: oxford university press, 1998.

cottingham, john, ed. the cambridge companion to descartes. cambridge, uk: cambridge university press, 1992.

descartes, rené. oeuvres de descartes, eds. charles adam and paul tannery. paris: cerf, 18971913

garber, daniel. descartes' metaphysical physics. chicago: university of chicago press, 1992.

gaukroger, stephen. descartes: an intellectual biography. oxford: clarendon press, 1995.

grimaldi, nicolas. six etudes sur la volonté et la liberté chez descartes. paris: vrin, 1988

hatfield, gary. "force (god) in descartes' philosophy." studies in the history and philosophy of science 10 (1979): 113-140.

jones, matthew. "descartes's geometry as spiritual exercise." critical inquiry 28 (2000): 40-71

marion, jean-luc. sur la theologie blanche de descartes. paris: presses universitaires de france, 1981

rorty, amélie oksenberg, ed. essays on descartes' meditations. berkeley and los angeles: university of california press, 1986.

rodis-lewis, genevieve. descartes. paris: librairie generale française, 1984.

anne a. davenport

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Descartes, Rene

RenÉ Descartes

Born: March 31, 1596
La Haye, France
Died: February 11, 1650
Stockholm, Sweden

French philosopher and writer

The French thinker René Descartes is called the father of modern philosophy (the study of the universe and man's place in it). His Discourse on Method and Meditations defined the basic problems of philosophy for at least a century.

Early life

René Descartes was born on March 31, 1596, in La Haye, France. His father, Joachim, served in the Parliament of Brittany, France. Jeanne Brochard Descartes, his mother, died in 1597. His father remarried and René and his older brother and sister were raised by their maternal grandmother and by a nurse for whom he retained a deep affection. In 1606 Descartes entered La Flèche, a religious college established for the education of the sons of noblemen. As a child he was often ill and was allowed to spend a portion of each day studying in bed. He used this time for meditation and thought. According to Descartes's description of his eight-year course of studies at La Flèche, he often felt embarrassed at the extent of his own ignorance.

Travel and study

After leaving college at age eighteen, Descartes earned a law degree in Poitiers, France. From 1618 to 1628 he traveled throughout Europe as a soldier. Living on income from inherited properties, Descartes served without pay and saw little action. He was present, however, at one of the major battles of the Thirty Years War (161848). Descartes sought out famous mathematicians, scientists, and philosophers (those who seek wisdom) wherever he traveled. The most significant of these friendships was with Isaac Beeckman, a Dutch mathematician, who encouraged Descartes to begin writing scientific theories on mathematics and music.

Descartes was deeply influenced by three dreams he had in 1619 in Ulm, Germany. He interpreted them to mean that all science is one and that its mastery is universal wisdom. This idea of the unity of all science was in opposition to the belief that the sciences were distinguished by their different objects of study. Descartes felt that if one could draw conclusions from a correct method of reasoning, then one could know everything. He began to devote his efforts to proving that he had discovered such a method. To focus better on his work, Descartes moved to Holland, where he lived peacefully for the next twenty years.

First works

Descartes's first major work, Rules for the Direction of the Mind, was written by 1629 but was not published until 1701. The work begins by assuming that man's knowledge has been limited by the belief that science is determined by the various objects of experience. The first rule therefore states that all true judgment depends on reason alone. For example, mathematical truths are valid even without observation and experiment. The second rule argues that the standard for true knowledge should be the certainty demanded of mathematical demonstrations. The third rule states that the mind should be influenced only by what can clearly be observed. The remaining rules are devoted to the explanation of these ideas or to showing their use in mathematical problems.

By 1634 Descartes had written The World, in which he supported several theories, including the idea of Nicolaus Copernicus (14731543) that Earth is not the center of the universe but revolves around the sun. Only fragments of the book survive, because when Descartes heard that a book published by Galileo (15641642), which also supported Copernicus, had been condemned by the Catholic Church, his fear of similar treatment led him to withdraw his work. In 1634 he also wrote the brief Treatise on Man, which attempted to explain human physiology (a branch of biology dealing with organs, tissues, and cells).

Other works

In 1637 Descartes finished Discourse on Method, which uses a personal account of his education as an example of the need for a new method of study. Descartes also presents four rules for reducing any problem to its basics and then constructing solutions. In 1641 and 1642 Meditations on First Philosophy appeared together with six sets of objections by other famous thinkers. The Meditations is one of the most famous books in the history of philosophy. While earlier Descartes works were concerned with explaining a method of thinking, this work applies that method to the problems of philosophy, including the convincing of doubters, the existence of the human soul, the nature of God, and the basis of truth.

The remainder of Descartes's career was spent defending his positions. In 1644 he published the Principles of Philosophy, which breaks down and expands the arguments of the earlier Meditations. In 1649 Descartes accepted an invitation from Queen Christina of Sweden (16261689) to become her teacher. During this time he wrote The Passions of the Soul, which explains passion as a product of physical and chemical processes. The weather in Sweden caused Descartes's health to suffer, however, and after a brief illness he died in Stockholm in 1650.

For More Information

Balz, Albert G. A. Descartes and the Modern Mind. New Haven, CT: Yale University Press, 1952.

Descartes, René. Descartes: Selected Philosophical Writings. Edited by John Cottingham. New York: Cambridge University Press, 1988.

Gaukroger, Stephen. Descartes: An Intellectual Biography. New York: Oxford University Press, 1995.

Rodis-Lewis, Geneviève. Descartes: His Life and Thought. Ithaca: Cornell University Press, 1998.

Strathern, Paul. Descartes in 90 Minutes. Chicago: Ivan R. Dee, Inc., 1996.

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Descartes, René

René Descartes (rənā´ dākärt´), Lat. Renatus Cartesius, 1596–1650, French philosopher, mathematician, and scientist, b. La Haye. Descartes' methodology was a major influence in the transition from medieval science and philosophy to the modern era.


Descartes was educated in the Jesuit College at La Flèche and the Univ. of Poitiers, then entered the army of Prince Maurice of Nassau. In 1628 he retired to Holland, where he spent his time in scientific research and philosophic reflection. Even before going to Holland, Descartes had begun his great work, for the essay on algebra and the Compendium musicae probably antedate 1628. But it was with the appearance in 1637 of a group of essays that he first made a name for himself. These writings included the famous Discourse on Method and other essays on optics, meteors, and analytical geometry. In 1649 he was invited by Queen Christina to Sweden, but he was unable to endure the rigors of the northern climate and died not long after arriving in Sweden.

Elements of Cartesian Philosophy

It was with the intention of extending mathematical method to all fields of human knowledge that Descartes developed his methodology, the cardinal aspect of his philosophy. He discards the authoritarian system of the scholastics and begins with universal doubt. But there is one thing that cannot be doubted: doubt itself. This is the kernel expressed in his famous phrase, Cogito, ergo sum [I think, therefore I am].

From the certainty of the existence of a thinking being, Descartes passed to the existence of God, for which he offered one proof based on St. Anselm's ontological proof and another based on the first cause that must have produced the idea of God in the thinker. Having thus arrived at the existence of God, he reaches the reality of the physical world through God, who would not deceive the thinking mind by perceptions that are illusions. Therefore, the external world, which we perceive, must exist. He thus falls back on the acceptance of what we perceive clearly and distinctly as being true, and he studies the material world to perceive connections. He views the physical world as mechanistic and entirely divorced from the mind, the only connection between the two being by intervention of God. This is almost complete dualism.

The development of Descartes' philosophy is in Meditationes de prima philosophia (1641); his Principia philosophiae (1644) is also very important. His influence on philosophy was immense, and was widely felt in law and theology also. Frequently he has been called the father of modern philosophy, but his importance has been challenged in recent years with the demonstration of his great debt to the scholastics. He influenced the rationalists, and Baruch Spinoza also reflects Descartes's doctrines in some degree. The more direct followers of Descartes, the Cartesian philosophers, devoted themselves chiefly to the problem of the relation of body and soul, of matter and mind. From this came the doctrine of occasionalism, developed by Nicolas Malebranche and Arnold Geulincx.

Major Contributions to Science

In science, Descartes discarded tradition and to an extent supported the same method as Francis Bacon, but with emphasis on rationalization and logic rather than upon experiences. In physical theory his doctrines were formulated as a compromise between his devotion to Roman Catholicism and his commitment to the scientific method, which met opposition in the church officials of the day. Mathematics was his greatest interest; building upon the work of others, he originated the Cartesian coordinates and Cartesian curves; he is often said to be the founder of analytical geometry. To algebra he contributed the treatment of negative roots and the convention of exponent notation. He made numerous advances in optics, such as his study of the reflection and refraction of light. He wrote a text on physiology, and he also worked in psychology; he contended that emotion was finally physiological at base and argued that the control of the physical expression of emotion would control the emotions themselves. His chief work on psychology is in his Traité des passions de l'âme (1649).


See biographies by J. R. Vrooman (1970), S. Gaukroger (1995), R. Watson (2002), A. C. Grayling (2005), and D. Clarke (2006); see studies by J. Maritain (tr. 1944, repr. 1969), A. G. Balz (1952, repr. 1967), H. Caton (1973), S. Gaukroger (1989 and 2002; as ed. 1980, 1998, 2000, and 2006), and S. Nadler (2013).

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Descartes, René

René Descartes

French philosopher and mathematician whose ideas included early and significant contributions to the field of psychology.

Descartes was born in France, near the small village of Le Haye. From the age of 10, he attended the most prestigious school in France, the Royal Collège of La Flèche, graduating at the age of 16. After spending some time sampling the amusements of Parisian society, followed by a period of solitary studies in philosophy and mathematics, Descartes briefly served as a soldier on the eve of the Thirty Years' War, joining first the Protestant and then the Catholic forces. Returning to the study of science and philosophy after the war, he spent several more years in Paris before moving to Holland at the age of 32. There Descartes wrote his most important works, Discourse on Method (1637), Meditations on First Philosophy (1642), and Principles of Philosophy (1644). Because his books aroused controversy among the Dutch Protestant clergy, Descartes, already wary after Galileo's condemnation by the Inquisition, published little for the remainder of his life, confining his thoughts largely to unpublished manuscripts and letters. His last published work was the Passions of the Soul (1649). Descartes remained in Holland for most of his life, although he moved frequently during his time there. In 1649, he left for Sweden at the invitation of Queen Christina and undertook to tutor her in philosophy. Only months after arriving in Sweden, Descartes died at the age of 53.

Descartes's philosophy is known for its glorification of human reason. He began with the premise that the only way to be sure of anything is to doubt everything ("I resolved to reject as false everything in which I could imagine the least doubt, in order to see if there afterwards remained anything that was entirely indubitable"). In so doing, Descartes arrived at the conclusion that the one thing he could be sure of was his own act of doubtinga mental process. From the certainty expressed in the famous statement, "I think, therefore I am," he built a philosophy that gave to the workings of the individual mind priority over both immediate sensory experience and received wisdom. Descartes postulated a radical mind-body dualism, claiming that the universe consisted of two utterly distinct substances: mind ("thinking substance" or res cogitans) and matter ("physical substance" or res extensa ). Thus, he separated mental phenomena from the comprehensive mechanistic explanation he gave for the workings of matter and material things, including the human body, which he divided into ten physiological systems. These included such faculties as memory and

imagination , along with the purely physiological functions of digestion, circulation, and respiration.

Descartes believed the primary site of interaction between mind and body to be the pineal gland (which he incorrectly thought to be unique to humans). He held that the will, an aspect of the mind, can move the pineal gland and cause the transmission of what he called animal spirits, which produce mechanical changes in the body; and, similarly, that changes in the body are transmitted to the pineal gland and can there affect the mind. His rationalistic ideas provided a basis for the Enlightenment and became the dominant system of philosophy until the work of David Hume (1711-1776) and Immanuel Kant (1724-1804). While many of Descartes's individual arguments have since been discredited, his overall view of the dualism between mind and body has been a powerful influence on succeeding generations of philosophers and psychologists.

Further Reading

Popper, K., and J. Eccles. The Self and Its Brain. London, 1977.

Smith, Norman Kemp. New Studies in the Philosophy of Descartes. New York: Russell and Russell, 1963.

Vrooman, J. R. Rene Descartes: A Biography. New York: Putnam, 1970.

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Descartes, René

Descartes, René (1596–1650) Together with Immanuel Kant and David Hume, the French philosopher René Descartes is one of the founding figures of modern Western philosophy. Descartes also made significant contributions to mathematics and the science of mechanics. He is best known for his Discourse on Method and Meditations, two texts in which he employed his method of systematic doubt so as to arrive at some indubitable foundation from which certain knowledge could be deduced. Famously, Descartes discovered he could doubt virtually everything, save that in doubting, and so thinking, he must at least exist. However, the existence thus asserted was not his bodily existence, but rather the existence of the self as a ‘thinking thing’. Descartes required proof of the existence of God, to restore his confidence in the existence of material bodies, defined by their spatial existence. This metaphysical view of the world as composed of extended material bodies, on the one hand, and souls or minds defined by thought, on the other, is known as dualism. Descartes himself, and successive dualist philosophers of mind, have experienced great difficulty in accounting coherently for the special connection between mind and body which constitutes the human person.

The influence of body–mind dualism is pervasive throughout the contemporary social sciences (for example, in Max Weber's distinction between behaviour and meaningful action). The increasingly problematic failure of sociology to deal adequately with either human embodiment or ecological issues is one legacy of this. Psychoanalysis and recent structuralist approaches in social science, which affect to ‘de-centre’ the human subject, often start out by explicitly rejecting Descartes's assumption of the ‘transparency’ of the self to reflection. Finally, Descartes is now frequently criticized as advocating a view of animals as non-conscious complex machines, thus allegedly excluding animals from direct moral concern, and sustaining an untenable gulf between human and animal nature. The adjective used to refer to Descartes is ‘Cartesian’. See also METAPHYSICS.

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Descartes, René

Descartes, René (1596–1650). Philosopher. Educated at the Jesuit college of La Flèche, in 1613 he went to Paris. Having devoted himself to philosophy, he settled in Holland. In 1649, at Queen Christina's invitation, he went to Sweden, where he died. His philosophy—expounded principally in his Meditations (1641), Principles (1644), and Discourse on Method (1637)—is based on a method of radical doubt. But even doubt leaves an awareness of self—his famous cogito ergo sum (‘I think, therefore I am’)—which becomes the pivot of his philosophy. From this point Descartes established, by pursuing ‘clear and distinct ideas’, a radical distinction (Cartesian dualism) between mind and matter—‘thinking’ and ‘extended’ reality—the existence of God (principally by a form of the ontological argument), and thence the reliability of the world perceived through the senses.

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Descartes, René

Descartes, René (1596–1650) French philosopher and mathematician. Often regarded as the father of modern philosophy. In 1619, he described an all-embracing science of the universe. His works include Discourse on Method (1637), Meditations on the First Philosophy (1641) and Principles of Philosophy (1644). Descartes' methods of deduction and intuition inform modern metaphysics. By doubting all his ideas, he reached one indubitable proposition: “I am thinking”, and from this that he existed: cogito ergo sum (“I think, therefore I am”). He also founded analytic geometry, introduced the Cartesian coordinate system and helped establish the science of optics.

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