René Descartes (1596-1650)

I. General Observations

René Descartes (picture) is justly considered the father of modern philosophy and the founder of the rational method as applied to philosophical research. In fact, he is the first philosopher to begin with the impressions which are in our intellect (intellectual phenomenalism) and lay down the laws which reason must follow in order to arrive at reasonably certain philosophical data.

This phenomenalism does not find its full development in Descartes. Indeed, Descartes reaches metaphysical conclusions which are no different from those of Scholastic philosophy. He maintains the transcendency of God, upholds human liberty and Christian morality.

But pantheism is sown deep in every form of immanentism. The rationalism of Descartes was to be quickly and logically bent in this direction by Spinoza, while other Cartesians, such as Malebranche and Leibniz, tried -- with less logic -- middle-of-the-road solutions between pantheism and the transcendence of God.

II. Life and Works

Descartes was born in 1596 at La Haye in France of a noble family, and was educated in the celebrated Jesuit college of La Flèche, where he received a philosophical and scientific education according to the principles of the Scholasticism of his day. Not fully satisfied with this first education, and urged on by a desire to better himself, he went first to Paris, and then enlisted in the army during the Thirty Years' War.

On the ninth of November, 1619, while still in the service in winter quarters, he gave himself up to meditating on how to apply the mathematical method of the sciences to philosophy. During this time he conceived the four laws which he described in his work Discourse on Method. He then abandoned the army, but before dedicating himself completely to philosophical meditation he undertook long travels throughout Europe.

In 1629 he retired to Holland, which offered him tranquillity for meditation and writing. He remained there until 1649. During these twenty years he wrote nearly all his books. In 1649 he went to the court of Queen Christina of Sweden, being summoned there by the Queen, who wished to study philosophy under his direction. Unable to resist the rigors of winter, he died in Sweden during 1650.

Descartes was a scientist and a philosopher. As a scientist he is noted for his studies in mechanics, physics and mathematics. As a philosopher he opened the period of modern philosophy.

Not all the philosophical works written by Descartes were published during his lifetime. His Rule for the Direction of the Mind was published posthumously, as was his treatise on The World.

The philosophical works published by the author were four: Discourse on Method; Meditations on First Philosophy, in which he proves the existence of God and the immortality of the soul; Principles of Philosophy, in four books, a systematic work reviewing the entire thought of the author; The Passions of the Soul, treating of the problem of morality.

III. The Laws of the Cartesian Method

Descartes, in his work Discourse on Method, after giving a criticism of the education which he had received (a criticism which is indirectly an attack on the Scholasticism of his day), goes on to set up the new method, according to him, must be the basis of all scientific and philosophical research.

These laws are four:

* To accept nothing as true that is not recognized by the reason as clear and distinct;
* To analyze complex ideas by breaking them down into their simple constitutive elements, which reason can intuitively apprehend;
* To reconstruct, beginning with simple ideas and working synthetically to the complex;
* To make an accurate and complete enumeration of the data of the problem, using in this step both the methods of induction and deduction.

To better understand these laws, we must note that for Descartes the point of departure is the ideas, clearly and distinctly known by the intellect -- the subjective impressions on the intellect. Beyond these clear and distinct ideas one cannot go, and hence the ultimate principle of truth consists in the clearness of the idea. Clear and distinct intuitions of the intellect are true. For Descartes, such clear and distinct intuitions are thought itself ("cogito") and the idea of extension.

Having arrived at this starting point (clear and distinct ideas), the intellect begins its discursive and deductive operation (represented by the second and third rules). The second law (called analysis) directs that the elementary notions be reunited with the clear and distinct ideas (the minor of the Scholastic syllogism). The third law (synthesis) presents them as the conclusion flowing from the premises. The final law (complete enumeration) stresses that no link in the deductive chain should be omitted and that every step should be logically deduced from the starting point (i.e., from the clear and distinct ideas). Thus, working from one step to the next, there will be achieved a system of truths all of which are clear and distinct, because all participate in the same degree of truth enjoyed by the first idea, which was clear and distinct.

This, as we know, is the method adopted in mathematics. Descartes transferred it to philosophy with the intention of finding clear and distinct concrete ideas, and of deducing from these, through reason alone, an entire system of truths which would also be real or objective.

The Aristotelio-Scholastic method (as well as that of classical realism in general) is also deductive, but it is very different from that of Descartes. Scholastic deduction is connected with objective reality because ideas are abstractions of the forms of the objects which experience presents. Thus both the concreteness of the ideas and the concreteness of the deductions based on these ideas are justified.

In Descartes ideas do not come from experience, but the intellect finds them within itself. Descartes declares that only these ideas are valid in the field of reality. Thus the concreteness (or the objective validity) of an idea is dependent upon its own clearness and distinction.

IV. Metaphysics: From Methodical Doubt to "Cogito Ergo Sum"

Descartes, as a result of the principles already established in his method, had first of all to seek out a solid starting point (a clear and distinct concrete idea), and from this opens his deductive process. To arrive at this solid starting point, he begins with methodical doubt, that is, a doubt which will be the means of arriving at certitude. This differs from the systematic doubt of the Skeptics, who doubt in order to remain in doubt.

I can doubt all the impressions that exist within my knowing faculties, whether they be those impressions which come to me through the senses or through the intellect. Indeed, I may doubt even mathematical truths, in so far as it could be that the human intelligence is under the influence of a malignant genius which takes sport in making what is objectively irrational appear to me as rational.

Doubt is thus carried to its extreme form. But notwithstanding this fact, doubt causes to rise in me the most luminous and indisputable certainty. Even presupposing that the entire content of my thought is false, the incontestable truth is that I think: one cannot doubt without thinking; and if I think, I exist: "Cogito ergo sum."

It is to be observed that for Descartes the validity of "Cogito ergo sum" rests in this, that the doubt presents intuitively to the mind the subject who doubts, that is, the thinking substance. In this, Cartesian doubt differs from that of St. Augustine ("Si fallor, sum"), which embodies a truth sufficiently strong to overcome the position of Skepticism. In Descartes, "Cogito ergo sum" is assumed, not only in order to overcome the Skeptic position but as a foundation for the primary reality (the existence of the "res cogitans"), from which the way to further research is to be taken.

This is the point which distinguishes the classic realistic philosophy from Cartesian and modern philosophy. With Descartes, philosophy ceases to be the science of being, and becomes the science of thought (epistemology). Whereas, at first, being conditioned thought, now it is thought that conditions being. This principle, more or less realized by the philosophers immediately following Descartes, was to reach its full consciousness in Kant and modern Idealism. (See: Meditations on First Philosophy, I and II; Discourse on Method, IV.)

V. From "Cogito" to the Proof of the Existence of God

The "cogito" reveals the existence of the subject, limited and imperfect because liable to doubt. It is necessary to arrive at an objective and perfect reality, i.e., to prove the existence of God.

Descartes makes use of three arguments which can be summarized thus:

* "Cogito" has given me a consciousness of my own limited and imperfect being. This proves that I have not given existence to myself, for in such a case I would have given myself a perfect nature and not the one I have, which is subject to doubt.
* I have the idea of the perfect: If I did not possess it, I could never know that I am imperfect. Now, whence comes this idea of the perfect? Not from myself, for I am imperfect, and the perfect cannot arise from the imperfect. Hence it comes from a Perfect Being, that is, from God.
* The very analysis of the idea of the perfect includes the existence of the perfect being, for just as the valley is included in the idea of a mountain, so also existence is included in the idea of the perfect. (the argument of St. Anselm). (See: Meditations on First Philosophy, V; Discourse on Method, IV.)

Regarding the nature of God, Descartes ascribes to it more or less the same attributes as does traditional Christian theistic thought. In Descartes, however, these attributes assume a different significance and value. God, above all, is absolute substance: the only substance, properly so-called (hence the way is open to the pantheism of Spinoza). An attribute which has great value for Descartes is the veracity of God.

God, the most perfect being, cannot be deceived and cannot deceive. Thus the veracity of God serves as a guarantee for the entire series of clear and distinct ideas. They are true because if they are not true, I, having proved the existence of God, would have to say that He is deceiving by creating a rational creature who is deceived even in the apprehension of clear and distinct ideas. Thus, with the proof of the existence of God, the hypothesis of a malignant genius falls of its own weight.

Regarding the origin of ideas, Descartes holds that the idea of God, all primitive notions, all logical, mathematical, moral principles, and so forth, are innate. God is the guarantee of the truth of these innate ideas. Alongside these innate ideas Descartes distinguishes two other groups of ideas:

* the adventitious, which are derived from the senses; and
* the fictitious, which are fashioned by the thinking subject out of the former.

Both groups are considered of little worth by Descartes because they do not enjoy the guarantee of the divine veracity, and hence are fonts of error. Only innate ideas and the rational deduction made from them have the value of truth. (See: Meditations on First Philosophy, III.)

Rene Descartes

Descartes was a "jack of all trades", making major contributions to the areas of anatomy, cognitive science, optics, mathematics and philosophy. Underlying his methodology is the belief that all science is based on mathematics. This is manifested in his unification of ancient geometry and his new alegbra based on the Cartesian coodinate system.

For Descartes, certainty in philosphy and in mathematics is gained through understanding. We may know that two apples and two apples makes four apples, but Descartes believes that matematics transcends the senses, contributing to an overall mathematical order to the universe that is independent of senses.

Senses were at the center of his Meditations on First Philosphy, a work in which Descartes explores the concepts of self, God and mind. He begins by shaking our belief in the sneses; if they are all an illusion created by a malicious deceiver, what can we trust? His answer is that we can doubt, and that the deceiver cannot cause us to doubt our own existence. Thus, the famous "cogito ergo sum" (I think therefore I am). However, the I is not a physical "i", is is an immaterial mind that is identified by "I".

Thus begins Cartesian Dualism, the theory that there are two fundamental types of entities : mind and matter. The physical bodies exists extended in space, with depth, width and breadth. However, minds are entirely immaterial and nonspatial; they are the "I" he refers to. Since the mind is the only entity that can think (rocks cannot), Descartes uses the cogito arguemnt to prove the existence of a mind.

Rene Descartes

Rene Descartes is one of the most important thinkers of the modern era. A pre-eminent French philosopher, mathematician and scientist, he is known as both the “Founder of Modern Philosophy” and the “Father of Modern Mathematics”. As a mathematician, Descartes invented the Cartesian coordinate system, which unified algebra with Euclidean geometry. In philosophy, Descartes was a major figure in 17th century continental rationalism, later advocated by Spinoza and Leibniz, and opposed by the empiricist school of thought, consisting of Hobbes, Locke, Berkeley, and Hume. Descartes’ most influential work, Meditations on First Philosophy, has inspired numerous contemporary debates in epistemology and philosophy of mind. There, Descartes is best known for employing methodological skepticism in an attempt to arrive at a fundamental set of principles that one can know as true without any doubt. Most famously, he established “I think therefore I am” (cogito ergo sum) as a proposition which he could not doubt.

Descartes, René (1596–1650)

René Descartes, often called the father of modern philosophy, attempted to break with the philosophical traditions of his day and start philosophy anew. Rejecting the Aristotelian philosophy of the schools, the authority of tradition and the authority of the senses, he built a philosophical system that included a method of inquiry, a metaphysics, a mechanistic physics and biology, and an account of human psychology intended to ground an ethics. Descartes was also important as one of the founders of the new analytic geometry, which combines geometry and algebra, and whose certainty provided a kind of model for the rest of his philosophy.

After an education in the scholastic and humanistic traditions, Descartes’ earliest work was mostly in mathematics and mathematical physics, in which his most important achievements were his analytical geometry and his discovery of the law of refraction in optics. In this early period he also wrote his unfinished treatise on method, the Rules for the Direction of the Mind , which set out a procedure for investigating nature, based on the reduction of complex problems to simpler ones solvable by direct intuition. From these intuitively established foundations, Descartes tried to show how one could then attain the solution of the problems originally posed.

Descartes abandoned these methodological studies by 1628 or 1629, turning first to metaphysics, and soon afterwards to an orderly exposition of his physics and biology in The World. But this work was overtly Copernican in its cosmology, and when Galileo was condemned in 1633, Descartes withdrew The World from publication; it appeared only after his death.

Descartes’ mature philosophy began to appear in 1637 with the publication of a single volume containing the Geometry, Dioptrics and Meteors, three essays in which he presented some of his most notable scientific results, preceded by the Discourse on the Method, a semi-autobiographical introduction that outlined his approach to philosophy and the full system into which the specific results fit. In the years following, he published a series of writings in which he set out his system in a more orderly way, beginning with its metaphysical foundations in the Meditations (1641), adding his physics in the Principles of Philosophy (1644), and offering a sketch of the psychology and moral philosophy in the Passions of the Soul (1649).

In our youth, Descartes held, we acquire many prejudices which interfere with the proper use of our reason. Consequently, later we must reject everything we believe and start anew. Hence the Meditations begins with a series of arguments intended to cast doubt upon everything formerly believed, and culminating in the hypothesis of an all-deceiving evil genius, a device to keep former beliefs from returning. The rebuilding of the world begins with the discovery of the self through the ‘Cogito Argument’ (‘I am thinking, therefore I exist’) – a self known only as a thinking thing, and known independently of the senses. Within this thinking self, Descartes discovers an idea of God, an idea of something so perfect that it could not have been caused in us by anything with less perfection than God Himself. From this he concluded that God must exist which, in turn, guarantees that reason can be trusted. Since we are made in such a way that we cannot help holding certain beliefs (the so-called ‘clear and distinct’ perceptions), God would be a deceiver, and thus imperfect, if such beliefs were wrong; any mistakes must be due to our own misuse of reason. This is Descartes’ famous epistemological principle of clear and distinct perception. This central argument in Descartes’ philosophy, however, is threatened with circularity – the Cartesian Circle – since the arguments that establish the trustworthiness of reason (the Cogito Argument and the argument for the existence of God) themselves seem to depend on the trustworthiness of reason.

Also central to Descartes’ metaphysics was the distinction between mind and body. Since the clear and distinct ideas of mind and body are entirely separate, God can create them apart from one another. Therefore, they are distinct substances. The mind is a substance whose essence is thought alone, and hence exists entirely outside geometric categories, including place. Body is a substance whose essence is extension alone, a geometric object without even sensory qualities like colour or taste, which exist only in the perceiving mind. We know that such bodies exist as the causes of sensation: God has given us a great propensity to believe that our sensations come to us from external bodies, and no means to correct that propensity; hence, he would be a deceiver if we were mistaken. But Descartes also held that the mind and body are closely united with one another; sensation and other feelings, such as hunger and pain, arise from this union. Sensations cannot inform us about the real nature of things, but they can be reliable as sources of knowledge useful to maintaining the mind and body unity. While many of Descartes’ contemporaries found it difficult to understand how mind and body can relate to one another, Descartes took it as a simple fact of experience that they do. His account of the passions is an account of how this connection leads us to feelings like wonder, love, hatred, desire, joy and sadness, from which all other passions derive. Understanding these passions helps us to control them, which was a central aim of morality for Descartes.

Descartes’ account of body as extended substance led to a physics as well. Because to be extended is to be a body, there can be no empty space. Furthermore, since all body is of the same nature, all differences between bodies are to be explained in terms of the size, shape and motion of their component parts, and in terms of the laws of motion that they obey. Descartes attempted to derive these laws from the way in which God, in his constancy, conserves the world at every moment. In these mechanistic terms, Descartes attempted to explain a wide variety of features of the world, from the formation of planetary systems out of an initial chaos, to magnetism, to the vital functions of animals, which he considered to be mere machines.

Descartes never finished working out his ambitious programme in full detail. Though he published the metaphysics and the general portion of his physics, the physical explanation of specific phenomena, especially biological, remained unfinished, as did his moral theory. Despite this, however, Descartes’ programme had an enormous influence on the philosophy that followed, both within the substantial group that identified themselves as his followers, and outside.

René Descartes

René Descartes was a philosopher whose work, La géométrie, includes his application of algebra to geometry from which we now have Cartesian geometry.

Descartes was educated at the Jesuit college of La Flèche in Anjou. He entered the college at the age of eight years, just a few months after the opening of the college in January 1604. He studied there until 1612, studying classics, logic and traditional Aristotelian philosophy. He also learnt mathematics from the books of Clavius. While in the school his health was poor and he was granted permission to remain in bed until 11 o'clock in the morning, a custom he maintained until the year of his death.

School had made Descartes understand how little he knew, the only subject which was satisfactory in his eyes was mathematics. This idea became the foundation for his way of thinking, and was to form the basis for all his works.

Descartes spent a while in Paris, apparently keeping very much to himself, then he studied at the University of Poitiers. He received a law degree from Poitiers in 1616 then enlisted in the military school at Breda. In 1618 he started studying mathematics and mechanics under the Dutch scientist Isaac Beeckman, and began to seek a unified science of nature. After two years in Holland he travelled through Europe. Then in 1619 he joined the Bavarian army.

From 1620 to 1628 Descartes travelled through Europe, spending time in Bohemia (1620), Hungary (1621), Germany, Holland and France (1622-23). He spent time in 1623 in Paris where he made contact with Mersenne, an important contact which kept him in touch with the scientific world for many years. From Paris he travelled to Italy where he spent some time in Venice, then he returned to France again (1625).

By 1628 Descartes tired of the continual travelling and decided to settle down. He gave much thought to choosing a country suited to his nature and chose Holland. It was a good decision which he did not seem to regret over the next twenty years.

Soon after he settled in Holland Descartes began work on his first major treatise on physics, Le Monde, ou Traité de la Lumière. This work was near completion when news that Galileo was condemned to house arrest reached him. He, perhaps wisely, decided not to risk publication and the work was published, only in part, after his death. He explained later his change of direction saying:-

... in order to express my judgement more freely, without being called upon to assent to, or to refute the opinions of the learned, I resolved to leave all this world to them and to speak solely of what would happen in a new world, if God were now to create ... and allow her to act in accordance with the laws He had established.

In Holland Descartes had a number of scientific friends as well as continued contact with Mersenne. His friendship with Beeckman continued and he also had contact with Mydorge, Hortensius, Huygens and Frans van Schooten (the elder).

Descartes was pressed by his friends to publish his ideas and, although he was adamant in not publishing Le Monde, he wrote a treatise on science under the title Discours de la méthode pour bien conduire sa raison et chercher la vérité dans les sciences. Three appendices to this work were La Dioptrique, Les Météores, and La Géométrie. The treatise was published at Leiden in 1637 and Descartes wrote to Mersenne saying:-

I have tried in my "Dioptrique" and my "Météores" to show that my Méthode is better than the vulgar, and in my "Géométrie" to have demonstrated it.

The work describes what Descartes considers is a more satisfactory means of acquiring knowledge than that presented by Aristotle's logic. Only mathematics, Descartes feels, is certain, so all must be based on mathematics.

La Dioptrique is a work on optics and, although Descartes does not cite previous scientists for the ideas he puts forward, in fact there is little new. However his approach through experiment was an important contribution.

Les Météores is a work on meteorology and is important in being the first work which attempts to put the study of weather on a scientific basis. However many of Descartes' claims are not only wrong but could have easily been seen to be wrong if he had done some easy experiments. For example Roger Bacon had demonstrated the error in the commonly held belief that water which has been boiled freezes more quickly. However Descartes claims:-

... and we see by experience that water which has been kept on a fire for some time freezes more quickly than otherwise, the reason being that those of its parts which can be most easily folded and bent are driven off during the heating, leaving only those which are rigid.

Despite its many faults, the subject of meteorology was set on course after publication of Les Météores particularly through the work of Boyle, Hooke and Halley.

La Géométrie is by far the most important part of this work. In [17] Scott summarises the importance of this work in four points:-

1. He makes the first step towards a theory of invariants, which at later stages derelativises the system of reference and removes arbitrariness.
2. Algebra makes it possible to recognise the typical problems in geometry and to bring together problems which in geometrical dress would not appear to be related at all.
3. Algebra imports into geometry the most natural principles of division and the most natural hierarchy of method.
4. Not only can questions of solvability and geometrical possibility be decided elegantly, quickly and fully from the parallel algebra, without it they cannot be decided at all.


Some ideas in La Géométrie may have come from earlier work of Oresme but in Oresme's work there is no evidence of linking algebra and geometry. Wallis in Algebra (1685) strongly argues that the ideas of La Géométrie were copied from Harriot. Wallis writes:-

... the Praxis was read by Descartes, and every line of Descartes' analysis bears token of the impression.

There seems little to justify Wallis's claim, which was probably made partly through patriotism but also through his just desires to give Harriot more credit for his work. Harriot's work on equations, however, may indeed have influenced Descartes who always claimed, clearly falsely, that nothing in his work was influenced by the work of others.

Descartes' Meditations on First Philosophy, was published in 1641, designed for the philosopher and for the theologian. It consists of six meditations, Of the Things that we may doubt, Of the Nature of the Human Mind, Of God: that He exists, Of Truth and Error, Of the Essence of Material Things, Of the Existence of Material Things and of the Real Distinction between the Mind and the Body of Man. However many scientists were opposed to Descartes' ideas including Arnauld, Hobbes and Gassendi.

The most comprehensive of Descartes' works, Principia Philosophiae was published in Amsterdam in 1644. In four parts, The Principles of Human Knowledge, The Principles of Material Things, Of the Visible World and The Earth, it attempts to put the whole universe on a mathematical foundation reducing the study to one of mechanics.

This is an important point of view and was to point the way forward. Descartes did not believe in action at a distance. Therefore, given this, there could be no vacuum around the Earth otherwise there was no way that forces could be transferred. In many ways Descartes's theory, where forces work through contact, is more satisfactory than the mysterious effect of gravity acting at a distance.

However Descartes' mechanics leaves much to be desired. He assumes that the universe is filled with matter which, due to some initial motion, has settled down into a system of vortices which carry the sun, the stars, the planets and comets in their paths. Despite the problems with the vortex theory it was championed in France for nearly one hundred years even after Newton showed it was impossible as a dynamical system. As Brewster, one of Newton's 19th century biographers, puts it:-

Thus entrenched as the Cartesian system was ... it was not to be wondered at that the pure and sublime doctrines of the Principia were distrustfully received ... The uninstructed mind could not readily admit the idea that the great masses of the planets were suspended in empty space, and retained their orbits by an invisible influence...

Pleasing as Descartes's theory was even the supporters of his natural philosophy, such as the Cambridge metaphysical theologian Henry More, found objections. Certainly More admired Descartes, writing:-

I should look upon Des-Cartes as a man most truly inspired in the knowledge of Nature, than any that have professed themselves so these sixteen hundred years...

However between 1648 and 1649 they exchanged a number of letters in which More made some telling objections, Descartes however in his replies making no concessions to More's points. More went on to ask:-

Why are not your vortices in the form of columns or cylinders rather than ellipses, since any point of the axis of a vortex is as it were a centre from which the celestial matter recedes with, as far as I can see, a wholly constant impetus? ... Who causes all the planets not to revolve in one plane (the plane of the ecliptic)? ... And the Moon itself, neither in the plane of the Earth's equator nor in a plane parallel to this?

In 1644, the year his Meditations were published, Descartes visited France. He returned again in 1647, when he met Pascal and argued with him that a vacuum could not exist, and then again in 1648.

In 1649 Queen Christina of Sweden persuaded Descartes to go to Stockholm. However the Queen wanted to draw tangents at 5 a.m. and Descartes broke the habit of his lifetime of getting up at 11 o'clock. After only a few months in the cold northern climate, walking to the palace for 5 o'clock every morning, he died of pneumonia.

Descartes' Life and Works

Descartes has been heralded as the first modern philosopher. He is famous for having made an important connection between geometry and algebra, which allowed for the solving of geometrical problems by way of algebraic equations. He is also famous for having promoted a new conception of matter, which allowed for the accounting of physical phenomena by way of mechanical explanations. However, he is most famous for having written a relatively short work, Meditationes de Prima Philosophia (Meditations On First Philosophy), published in 1641, in which he provides a philosophical groundwork for the possibility of the sciences.
1. Early Years

Descartes was born in La Haye on March 31, 1596 of Joachim Descartes and Jeanne Brochard. He was one of a number of surviving children (two siblings and two half-siblings). His father was a lawyer and magistrate, which apparently left little time for family. Descartes's mother died in May of the year following his birth, and he, his full brother and sister, Pierre and Jeanne, were left to be raised by their grandmother in La Haye. At around ten years of age, in 1606, he was sent to the Jesuit college of La Fleche. He studied there until 1614, and in 1615 entered the University of Poitiers, where a year later he received his Baccalaureate and License in Canon & Civil Law. For the history and the text of his thesis, see the following supplementary document:

Descartes' Law Thesis

In 1618, at the age of twenty-two, he enlisted in the army of Prince Maurice of Nassau. It is not known what his duties were exactly, though Baillet suggests that he would have very likely been drawn to what would now be called the Corps of Engineers (Baillet, Livre 1, Chapitre 9, p. 41). This division would have engaged in applied mathematics, designing a variety of structures and machines aimed at protecting and assisting soldiers in battle. Sorell, on the other hand, notes that in Breda, where Descartes was stationed, the army "doubled as military academy for young noblemen on the Continent" (Sorell, p. 6). And, Gaukroger notes that the education of the young noblemen was structured around the educational model of Lipsius (1547-1606), a highly respected Dutch political theorist who received a Jesuit education at Cologne (Gaukroger, pp. 65-6). It is likely that the military environment (that is, the academy) at Breda would have reminded Descartes of La Fleche. Though there are reasons for thinking that he may have been a soldier, the majority of biographers argue that it is more likely that his duties were oriented more towards education or engineering.

While stationed at Breda, Descartes met the mathematician Isaac Beeckman (1588-1637). Notes that Descartes kept related to his correspondence reveal that he and Beeckman had become more than simple acquaintances-their relationship was more one of teacher and student (Descartes being the latter). This relationship would rekindle in Descartes an intense interest in the sciences. In addition to discussions about a wide variety of topics in natural science, a direct result of certain questions posed by Beeckman compelled Descartes to write the Compendium Musicae. Among other things, the Compendium attempted to work out a theory of harmony, rooted in the concepts of proportion or ratio, which (along the lines of the ancients) attempted to express the notion of harmony in mathematical terms. It would not be published during Descartes's lifetime. As for Beeckman, Descartes would later downplay his influence.
2. The World and Discourse

After Descartes left the army, in 1619, his whereabouts for the next few years are unknown. Based on what he says in the Discours de la Methode (Discourse on the Method), published in 1637, there is speculation that he spent time near Ulm (Descartes apparently attended the coronation of Ferdinand II in Frankfurt in 1619). There is some evidence that would suggest that he was in France in 1622, for it was at this time that property he had inherited was sold-the proceeds of which would provide him a simple income for many years. There is some speculation that between 1623 and 1625 he visited Italy. Descartes emerges in 1625 in Paris, his notes revealing that he was in contact with Father Marin Mersenne (1588-1648), a member of the Order of Minims. This relationship would prompt Descartes to make public his thoughts on natural philosophy (science). It is by way of Mersenne that Descartes's work would find its way into the hands of some of the best minds living in Paris-for instance, Antoine Arnauld (1612-1694), Pierre Gassendi (1592-1655), and Thomas Hobbes (1588-1679).

In 1628 Descartes left Paris. At this time he seems to have been working on the Regulae ad Directionem Ingenii (Rules for the Direction of the Mind), a work that he would abandon, some speculating around the time of the move from Paris. In 1630 he moved to Amsterdam. There he worked on drafts of the Dioptrique (the Optics) and the Meteors (the Meteorology), which were very likely intended to be a part of a larger work, Le Monde (The World). In 1632 he moved again, this time to Deventer, to apparently teach Henry Reneri (1593-1639) his physics. It is also during his stay in Deventer that Descartes probably worked on a final draft of the Traite de l'homme (Treatise on Man), which in connection to the Optics and the Meteorology was probably originally intended to be a part of The World.

When The World had become ready for publication in 1633, upon hearing of the Church's condemnation of Galileo (1564-1642) in the same year, Descartes decided against its publication. For, the world system he had adopted in the book assumed, as did Galileo's, the heliocentric Copernican model. In a letter to Mersenne, dated November 1633, Descartes expresses his fear that were he to publish The World, the same fate that befell Galileo would befall him. And, this is something that he understandably wanted to avoid. The World appears to have been constituted of several smaller, but related, works: a treatise on physics, a treatise on mechanics (machines), a treatise on animals, and a treatise on man. Although much of The World has been lost, some of it seems to have survived in the form of essays attached to the Discourse which, as was mentioned earlier, would be published four years later, in 1637. And, some of it was published posthumously. Arguably, Constantijn Huygens (1596-1687) received what Descartes refers to as "three sheets" of The World, along with a letter dated 5 October 1637. These "sheets" deal primarily with mechanics.

Around 1635, Reneri began to teach "Cartesian" physics. Also during this year, a domestic servant by the name of Helene gave birth to a baby girl, Francine. According to a baptismal record, dated 28 July 1635, Descartes is named the father (AT I 395n). Gaukroger gives the baptismal date as 7 August 1635 (Gaukroger, p. 294). And, Genevieve Rodis-Lewis gives Francine's date of birth as 19 June 1635 (Rodis-Lewis, p. 40). In 1636 Reneri acquired an official chair in Philosophy at the University of Utrecht, and continued to build a following of students interested in Cartesian science. Around March of 1636, at the age of forty, Descartes moved to Leiden to work out the publishing of the Discourse. And, in 1637 it is published. With the Discourse out and a following of students building in Utrecht, Descartes seems to have turned his attention from career to family. In a letter dated 30 August 1637 we find him apparently working out an arrangement for Francine, but strangely refers to her as his "niece"-which suggests that he did not want certain people to know that he was a father. Gaukroger suggests that despite this apparent denial of paternity, Descartes not only corresponds with Francine, but in 1637 brings her and Helene to his new home at Santpoort or Egmond-Binnen (Gaukroger, pp. 294, 332).

The Discourse is the first published work of Descartes's, coming some four years after his abandonment of the publishing of The World. This work is important for many reasons. For instance, it tells us what Descartes himself seems to have thought of his early education, and in particular, his early exposure to mathematics. Roger Ariew suggests that these reflections are not so much those of the historical Descartes, as much as they are those of a persona Descartes adopts in telling the story of the Discourse (Ariew, pp. 58-63). Uncontested, however, is the view that the Discourse sketches out the metaphysical underpinnings of the Cartesian system. And, as a bonus, it has three works that are attached to it that are apparently added so as to exemplify the method of inquiry it develops (though admittedly it is unclear how the method is applied in these essays). The attached essays are the Optics, the Meteorology, and Le Geometrie (the Geometry). As was suggested earlier, the Optics and Meteorology were very likely versions of works originally intended for The World.

It should be stressed that the three attached essays are important independent of the Discourse, for they contain much worth studying. In the Optics, for example, Descartes works out his laws of refraction, and within this context, what would later be called Snell's Law (which Descartes seems to have worked out as early as 1632). Further, although the Geometry would seem to have come out of nowhere, there is evidence in Descartes's notes to himself, from which Clerselier reconstructed some of Descartes's correspondence, that he had been working on some version of it as early as 1619. In a letter to Beeckman, dated 26 March 1619, for example, Descartes discusses the subject matter that is found in the Geometry, and in a letter dated 23 April 1619, he explicitly mentions the book's title. It is in this work that Descartes shows how certain geometrical problems can be solved by way of algebraic equations.

The significance of the sort of connection that Descartes made between geometry and algebra was great indeed, for without it the mathematization of the physics and the development of the calculus might not have happened when they did-a generation later via Sir Isaac Newton (1642-1727). It should be noted, however, that as groundbreaking as this work may be, contrary to the claims of many, nowhere in the Geometry is a "Cartesian Coordinate System" ever developed (that is, the x-y coordinate system taught to today's students of algebra), nor is he the originator of other mathematical concepts that bear his name, for example, the "Cartesian Product". Carl Boyer notes that various concepts that lead to analytic geometry are found for the first time in the Geometry, and that the Geometry's mathematical notation is still used today. But, he argues, although Cartesian geometry is taken by many to be synonymous with analytic geometry, the fact is that the fundamental aim of Descartes's system is quite different from that of contemporary analytic geometry (Boyer, pp. 370-1). And so, the claim that Descartes is the originator of analytic geometry, at least as we understand it today, overstates the case. As Boyer rightly points out, however, this does not diminish the importance of the work in the history of mathematics.
3. The Meditations

In 1639 Descartes began writing the Meditations. And, in 1640 he returned to Leiden to help work out its publication. During the year, Francine died. Understandably, Descartes was deeply saddened by her death. There is evidence to suggest that he was called away from Leiden around the time of her death, returning soon after. Some have speculated that he left Leiden to be at her side. Also during this year, Descartes's father and sister died. Descartes's relationship with his father (and brother) was of the sort that Pierre, his brother, failed to even bother him with the news of their father's death. Rather, it seems to have been in a letter from Mersenne that Descartes first learns of it. In a follow up letter to Mersenne, dated 3 December 1640, Descartes expresses regret in not having been able to see his father before his death. But, he refuses to leave Leiden to attend his father's funeral, and instead stays to complete the publishing of the Meditations. Some have suggested that this in part demonstrates a profound strain that existed in the relationship between Descartes and his father.

Today, the Meditations is by far Descartes's most popular work—though this would not have been the case in Descartes's day. This work is important to today's scholar for many reasons, the least of which is its including as an attached text written objections from some of the best minds living in Paris. Mersenne sent the Meditations to philosophers and theologians for criticism. The list of critics includes: Caterus, Hobbes, Arnauld, Gassendi, and Mersenne himself, with several other unnamed readers who raised their objections through Mersenne. A later edition would include Bordin. Descartes replied to each critic, and the result was an appended text referred to as "The Objections and Replies." The second edition contains seven sets in all.

The Meditations opens by developing skeptical questions concerning the possibility of knowledge. Through a series of several carefully thought out meditations, the reader establishes (along with the author) the groundwork for the possibility of knowledge (scientia). Descartes is not a skeptic, as some have insisted, but uses skepticism as a vehicle to motivate his reader to "discover" by way of philosophical investigation what constitutes this ground. In the Second Replies, Descartes refers to this style of presentation as the "analytic" style. There were two styles of presentation: analytic and synthetic. It is important not to confuse these terms with those, say, used by Kant. For Descartes the analytic style of presentation (and inquiry) proceeds by beginning with what is commonly taken to be known and discovering what is necessary for such knowledge. Thus, the inquiry moves from what is commonly known to first principles. The "discovery" moves in such a way that each discovery is based on what was discovered before. By contrast, the synthetic style of presentation begins by asserting first principles and then to determining what follows. Prompted by Mersenne, Descartes sketches out in the Second Replies a synthetic rendering of the Meditations.

In establishing the ground for science, Descartes was at the same time overthrowing a system of natural philosophy that had been established for centuries-a qualitative, Aristotelian physics. In a letter to Mersenne, dated 28 January 1641, Descartes says "these six meditations contain all the foundations of my physics. But please do not tell people, for that might make it harder for supporters of Aristotle to approve them. I hope that readers will gradually get used to my principles, and recognize their truth, before they notice that they destroy the principles of Aristotle." Unlike his earlier work, The World, the Meditations parts ways with the "old" science without explicitly forwarding controversial views, like that of the Copernican heliocentric model of the solar system. Specifically, the Cartesian view denies that physics is grounded in hot, cold, wet, and dry. It argues that contrary to Aristotle's view, such "qualities" are not properties of bodies at all. Rather, the only properties of bodies with which the physicist can concern him or herself are size, shape, motion, position, and so on-those modifications that conceptually (or logically) entail extension in length, breadth, and depth. In contrast to Aristotle's "qualities," the properties (or modes) of bodies dealt with in Cartesian physics are measurable specifically on ratio scales (as opposed to intensive scales), and hence are subject in all the right ways to mathematics (Buroker, pp. 596-7). This conception of matter, conjoined with the sort of mathematics found in the Geometry, allies itself with the work of such Italian natural philosophers as Tartaglia, Ubaldo, and Galileo, and helps further the movement of early thinkers in their attempts to establish a mathematical physics.

Descartes's letter to the "learned and distinguished men" of the Sorbonne, which is appended to the Meditations, suggests that he was trying to pitch the Meditations as a textbook for the university. Though the endorsement of the Learned Men would not have guaranteed that the Meditations would be accepted or used as a textbook, it could certainly be viewed as an important step to getting it accepted. Unlike today's notion of a textbook, in Descartes's day "textbooks" were intended mostly for teachers, not students. Typically, at the close of a teacher's career, his notes would be published for the benefit of those who would go on to teach such course material. The awkwardness of Descartes's seeking the acceptance and use of his Meditations by teachers is amplified by the fact that he was not a teacher himself. Consequently, his seeking "textbook" status would have very likely been viewed by those Learned Men as being a bit pretentious. He was, it could be said, a freelancer with no academic or political ties to the university (outside of his connection to Mersenne). And, he certainly lacked the credentials and reputation of someone like a Eustachius, whose widely used textbook of the period is of the sort the Meditations was in all likelihood aimed at replacing. Although the Meditations seems to have been endorsed by the Sorbonne, it was never adopted as a text for the university.
4. The Principles

Soon after his encounter with the Sorbonne, Descartes's public life was further complicated by the Dutch theologian, Gisbert Voetius (1588-1676). Voetius had attacked Regius, a Dutch physician who taught medicine at the University of Utrecht, for his having taught certain "Cartesian" ideas that conflicted with traditional theological doctrine. Regius was friend to both Reneri and Descartes, and was a strong adherent to Descartes's philosophical views. Voetius tried to have Regius removed from his position as professor, and attacked not only Descartes's work but his character. In his defense Descartes entered into the debate. The controversy would leave Regius confined to teaching medicine, and his published defense of (his conception of) Cartesian thought would be officially condemned by Voetius, who in five years time would rise to the position of University rector. At the end of the debate, which off and on lasted about five years, the situation ultimately became desperate for Descartes. He feared being expelled from the country and of seeing his books burned. He would even seek protection by asking the Prince of Orange to intervene and quell Voetius' attack.

In 1643, at the age of forty-seven, Descartes moved to Egmond du Hoef. With the Voetius controversy seemingly behind him (though, as mentioned above, it would again raise its head and climax five years down the road), Descartes and Princess Elizabeth of Bohemia began to correspond. In this exchange, Princess Elizabeth probed Descartes on the implications of his commitment to mind-body dualism. During this time, he completed a final draft of a new textbook, which he had begun three years earlier, the Principia Philosophiae (Principles of Philosophy), and in 1644 it was published. He dedicated it to Princess Elizabeth.

The Principles is an important text. The work is divided into four Parts, with five hundred and four articles. Part One develops Descartes's metaphysics. Although it would appear to be a quick run through of the Meditations, there are a number of dissimilarities. For example, the order of presentation of the proofs for God's existence, which some have argued is significant, found in the Third and Fifth Meditations, is reversed in the Principles. The principles introduced in Part Two are based on the metaphysics of Part One. And, the subsequent physics developed in Parts Three and Four is based upon the principles of Part Two. Although the physics turns out to be unsound, the Principles nevertheless inspired such great thinkers as Robert Boyle (1627-1691), Edmond Halley (1656-1742), and Isaac Newton. As an important side note, it must be stressed that even though Descartes had throughout his career put a great deal of emphasis on mathematics, the physics developed in the Principles does not appear to be a mathematical physics. Rather, it it traditionally taken to be a conceptual project with only a hint of empirical overtones-a physics rooted entirely in metaphysics. Arguably, however, Descartes's work on enumeration, order and measure, in the Rules provides the conceptual machinery necessary for establishing a ‘mathematical’ physics—a conceptual machinery that is carried over to the Principles (Smith 2003). Two parts, never completed, were originally intended to deal with plants, animals, and man. In light of this and what Descartes says in a 31 January 1642 letter to the mathematician Constantijn Huygens, it is plausible to think that the Principles would have looked something like The World had it been completed as planned.

One of the more controversial positions the Principles forwarded, at least according to Newton, was that a vacuum was impossible. This followed from Descartes's commitment to the view that the essence of body was extension. Supposing that a vacuum was taken to be a "gap" between bodies—that is, it is taken to be an utter absence of body (matter)-if it turned out (as indeed it does) that this gap was extended in length, breadth, and depth, then it would not be an absence of body, but would by definition be a body-as much a body as the two bodies between which it is taken to be a gap. The corporeal universe was thus a plenum, individual bodies separated only by their surfaces. Newton argued in his De Gravitatione and Principia that the concept of motion becomes problematic if the universe is taken to be a plenum. Another controversial position was Descartes's insistence that matter is infinitely divisible. Gassendi, and later Cordemoy, argued that there must be a bottom, a ‘substance,’ to the physical universe upon which the being of all corporeal things depend. In line with the ancient atomist Epicurus, they argued that if matter was infinitely divisible, so dividing it would show that there was no bottom—and so, corporeality would not be substantial. So, if corporeality is substantial, as Descartes himself had claimed, there must be a minimum measure of extension that could not be divided (by natural means, anyway). And so, there are atoms. But, this conclusion was something that Descartes explicitly rejected in the Principles.
5. The Passions

In 1646, as a result of the probings of Princess Elizabeth, Descartes completed a working draft of Passions de l'ame (Passions of the Soul). During this year another prominent political figure began to correspond with Descartes, Queen Christina of Sweden. And, Regius published what he took to be a new and improved version of Cartesian science, which as we now know would draw the wrath of Voetius. But Regius did not stop there, for he seemed to have found important differences between his "Cartesian" view and that of Descartes's, and attempted to separate the two, publishing a broadsheet that listed twenty-one anti-Cartesian theses (which his version of "Cartesian" science rejected). In response to this, Descartes wrote a single-page printed defense that was posted on public kiosks for all to read. Published in 1648, the Notae in Programma Quoddam (Notes on a Program-also referred to as Comments on a Certain Broadsheet) is Descartes's public defense. However, as mentioned earlier, tensions mounted as a result of the public exchange and Descartes felt his way of life in the Netherlands to be threatened. As luck would have it, an admirer and friend of Descartes's-Chanut, who worked for Queen Christina's court-and Queen Christina herself began probing Descartes about the possibility of coming to Sweden. And, after a not too lengthy correspondence, Queen Christina offered Descartes a position in her court. For many reasons, which would certanily include those related to his concerns about Voetius, Descartes accepted the offer. And, in 1649 he left for Sweden.

Queen Christina at first required very little from Descartes. However, according to Gaukroger, this would change. For, after he had some time to settle in, she ordered him to do two things: first, to put all of his papers in order, and secondly, to put together designs for an academy (Gaukroger, p. 415). Arguably, Descartes had some idea of how the latter might be done by way of his experience in Breda. In January of 1650 Queen Christina began to require Descartes to give her lessons in philosophy. These apparently would begin at five in the morning and would last for about five hours. They were given three days a week (Gaukroger, p. 415). During this time Descartes published the Passions, the work having emerged primarily from his correspondence with Princess Elizabeth (to whom he had dedicated the Principles). One aim of the Passions was to explain how the emotional (and thus moral) life of a human being was connected to the soul's being essentially united to a body. Simply put, a ’passion of the soul’ is a mental state (or thought) that arises as a direct result of brain activity. Such passions can move us to action. Since this is so, Descartes suggests that one needs to learn to control one's passions, for they can move one to perform vicious acts. Critics of Descartes, including Elizabeth, argued that Descartes's metaphysical commitments put real pressure on the view expounded in the Passions. For, according to Descartes's metaphysics, the nature of mind is to think and the nature of body is to be extended in length, breadth, and depth. One view concerning causation, a view that Descartes's critics seemed to have attributed to him, is that one thing causes another to move, for example, by way of contact. Contact, in this context, seems to be possible only by way of surfaces. Now, bodies, since they are extended and thus have surfaces, can come into contact with one another and thus can cause one another to move. However, if minds are not extended, they lack surfaces. And, if they lack surfaces, there is no way in principle for bodies to come into contact with them. Thus, there is no way in principle for bodies to move minds, and visa versa. That is, minds and bodies cannot in principle causally interact. And so, if the view expounded in the Passions requires that bodies and minds be capable of causal interaction, and Descartes's metaphysical commitments make such interaction impossible, Descartes's metaphysics puts a great deal of pressure on the view expounded in the Passions.

Although things seemed to be moving forward, they were not going as well as one would have hoped. In a letter to Bregy, for instance, dated 15 January 1650, Descartes expresses reservations about his decision to come to Sweden. He sees himself to be "out of his element," the winter so harsh that "men's thoughts are frozen here, like the water" (AT V 467; CSMK III 383). Given the sentiment expressed in the letter, this remark was probably intended to be as much Descartes's take on the intellectual climate as it was about the weather. In early February, less than a month after writing Bregy, Descartes fell ill. His illness quickly turned into a serious respiratory infection. And, although at the end of a week he appeared to have made some movement towards recovery, things took a turn for the worse and he died in the early morning of 11 February 1650. He was fifty-three years old.

RENE DESCARTES (1595-1650)

Rene Descartes was a famous French mathematician, scientist and philosopher. He was arguably the first major philosopher in the modern era to make a serious effort to defeat skepticism. His views about knowledge and certainty, as well as his views about the relationship between mind and body have been very influential over the last three centuries.

Descartes was born at La Haye (now called Descartes), and educated at the Jesuit College of La Flèche between 1606 and 1614. Descartes later claimed that his education gave him little of substance and that only mathematics had given him certain knowledge. In this lament he joins a chorus of seventeenth century philosophers including Bacon, Hobbes and Locke. In 1618 he went to Holland to serve in the army of Prince Maurice of Nassau, in travelled to Germany with that army. On the night of Nov ember 10, he had a series of dreams which he interpreted as signs that he would found a universal science. The most important influence on Descartes at this time was the mathematician Issac Beeckman, who stimulated Descartes by posing a number of problem s and discusiing issues in physics and mathematics with him. His first substantial work was the Regulae or Rules for the Direction of Mind written in 1628-9 but not published until 1701. This work shows Descartes interest in method which he shared with many sixteenth and seventeenth century scientists, mathematicians and philosophers.

One source of this interest in method was ancient mathematics. The thirteen books of Euclid's Elements was a model of knowledge and deductive method. But how had all this been achieved? Archimedes had made many remarkable discoveries. How had he come to make these discoveries? The method in which the results were presented (sometimes called the method of synthesis) was clearly not the method by which these results were discovered. So, the search was on for the method used by the ancient mathematicians to make their discoveries (the method of analysis). Descartes is clearly convinced that the discovery of the proper method is the key to scientific advance. For a more extended and detailed discussion of these methods, see John Cottingham , The Rationalists, Oxford University Press, Oxford, 1982. Chapter 2.

In November 1628 Descartes was in Paris, where he made himself famous in a confrontation with Chandoux. Chandoux claimed that science could only be based on probablitiies. This view reflected the dominance in French intellectual circles of Renaissance skepticism. This skptical view was rooted in the religious crisis in Europe resulting from the Protestant Reformation and had been deepened by the publication of the works of Sextus Empiricus and reflections on disagreements between classical authors. It was strengthend again by considerations about the differences in culture between New World cultures and that of Europe, and by the debates over the new Copernican system. All of this had been eloquently formulated by Montaigne in his Apology for Raymond Sebond and developed by his followers. Descartes attacked this view, claiming only that certainty could serve as a basis for knowledge, and that he himself had a method for attaining such certainty. In the same year Descartes moved to Holland where he remained with only brief interruptions until 1649.

In Holland Descartes produced a scientific work called Le Monde or The World which he was about to publish in 1634. At the point, however, he learned that Galileo had been condemned by the Church for teaching Copernicanism. Descarte s' book was Copernican to the core, and he therefore had it supressed. In 1638 Descartes published a book containing three essays on mathematical and scientific subjects and the Discourse on Method. These works were written in French (rather th an Latin) and were aimed at the educated world rather than simply academics. In 1641 Descartes followed this with the Meditationes de Prima Philosophia (Meditations on First Philosophy). This short work is more metaphysical than scientific, and aims to establish the certain foundations for the sciences which Descartes had announced in his confrontation with Chandoux in 1628. (For a more detailed account of this work see Structure of the Meditations. The work was published together with Objections and Replies from a six (and then seven) philosophers and theologians, including Thomas Hobbes, Pierre Gassendi and Antoine Arnauld.

After the Meditations, Descartes produced The Principles of Philosophy in 1644, the most complete statement of his mature philosophy and of the Cartesian system in general. Part 1 explains Descartes metaphysical views. Part II gives a detailed exposition of the principles of Cartesian physics. Part III applies those principles of physics to give a detailed explanation of the universe, and Part IV deals with a wide variety of terrestial phenomena. Two more parts were planned, to deal with pl ants and animals and man, but were not completed. In 1648 Descartes published "Notes against a Program" -- a response to a pamphlet published anonymously by Henricus Regius, Professor of Medecine at the University of Utrecht. Regius had been an early and enthusiastic supporter of Descartes. But when Regius published his Foundations of Physics Descartes complained that Regius had shamelessly used unpublished papers of Descartes to which he had access and had distorted Descartes' ideas. The "Notes" both illustrate the kind of academic controversies in which Descartes was involved during this decade, but also provides some insight into his views about mind and his doctrine of innate ideas.

Descartes last work Les Passions de l'áme was written as a result of the correspondence which Descartes carried on with Princess Elisabeth of Bohemia. The work was written in French, and published in Amsterdam and Paris in 1649. This work (like the Principles) is composed of a large number of short articles. Princess Elisabeth had raised the question of how the soul could interact with the body in 1643. In response to Elisabeth's questions, Descartes wrote a short work which developed into the Passions of the Soul. The work is a combination of psychology, physiology and ethics, and contains Descartes' theory of two way causal interaction via the pineal gland.

Two months before the publication of the Passions Descartes set sail for Stockholm, Sweden, at the invitation of Queen Christina of Sweden. Descartes' death in Stockholm of pneumonia, has regularly been attributed to the rigours of the Swedish climate and the fact that Descartes (no early riser) was sometimes required to give the Queen lessons as early as five in the morning. However unpleasant these conditions may have been, it seems plain that Descartes acquired his fatal malady as a result of nursing his friend the French ambassador (who had pneumonia) back to health.

René Descartes

While the great philosophical distinction between mind and body in western thought can be traced to the Greeks, it is to the seminal work of René Descartes (1596-1650) [see figure 1], French mathematician, philosopher, and physiologist, that we owe the first systematic account of the mind/body relationship. Descartes was born in Touraine, in the small town of La Haye and educated from the age of eight at the Jesuit college of La Flèche. At La Flèche, Descartes formed the habit of spending the morning in bed, engaged in systematic meditation. During his meditations, he was struck by the sharp contrast between the certainty of mathematics and the controversial nature of philosophy, and came to believe that the sciences could be made to yield results as certain as those of mathematics.

From 1612, when he left La Flèche, until 1628, when he settled in Holland, Descartes spent much of his time in travel, contemplation, and correspondence. From 1628 until his ill-fated trip to Sweden in 1649 he remained for the most part in Holland, and it was during this period that he composed a series of works that set the agenda for all later students of mind and body. The first of these works, De homine [1] was completed in Holland about 1633, on the eve of the condemnation of Galileo. When Descartes' friend and frequent correspondent, Marin Mersenne, wrote to him of Galileo's fate at the hands of the Inquisition, Descartes immediately suppressed his own treatise. As a result, the world's first extended essay on physiological psychology was published only well after its author's death.


[Figure 2] In this work, Descartes proposed a mechanism [see figure 2] for automatic reaction in response to external events. According to his proposal, external motions affect the peripheral ends of the nerve fibrils, which in turn displace the central ends. As the central ends are displaced, the pattern of interfibrillar space is rearranged and the flow of animal spirits is thereby directed into the appropriate nerves. It was Descartes' articulation of this mechanism for automatic, differentiated reaction that led to his generally being credited with the founding of reflex theory.

Although extended discussion of the metaphysical split between mind and body did not appear until Descartes' Meditationes, his De homine outlined these views and provided the first articulation of the mind/body interactionism that was to elicit such pronounced reaction from later thinkers. In Descartes' conception, the rational soul, an entity distinct from the body and making contact with the body at the pineal gland, might or might not become aware of the differential outflow of animal spirits brought about through the rearrangement of the interfibrillar spaces. When such awareness did occur, however, the result was conscious sensation -- body affecting mind. In turn, in voluntary action, the soul might itself initiate a differential outflow of animal spirits. Mind, in other words, could also affect body.

The year 1641 saw the appearance of Descartes' Meditationes de prima philosophia, in quibus Dei existentia, & animae à corpore distinctio, demonstratur


[Figure 3] In 1649, on the eve of his departure for Stockholm to take up residence as instructor to Queen Christina of Sweden, Descartes sent the manuscript of the last of his great works, Les passions de l'ame[3], to press. Les passions [see figure 3] is Descartes' most important contribution to psychology proper. In addition to an analysis of primary emotions, it contains Descartes' most extensive account of causal mind/body interactionism and of the localization of the soul's contact with the body in the pineal gland. As is well known, Descartes chose the pineal gland because it appeared to him to be the only organ in the brain that was not bilaterally duplicated and because he believed, erroneously, that it was uniquely human.

In February of 1650, returning in the bitter cold from a session with Queen Christina, who insisted on receiving her instruction at 5 a.m., Descartes contracted pneumonia. Within a week, the man who had given direction to much of later philosophy was dead. By focusing on the problem of true and certain knowledge, Descartes had made epistemology, the question of the relationship between mind and world, the starting point of philosophy. By localizing the soul's contact with body in the pineal gland, Descartes had raised the question of the relationship of mind to the brain and nervous system. Yet at the same time, by drawing a radical ontological distinction between body as extended and mind as pure thought, Descartes, in search of certitude, had paradoxically created intellectual chaos.