You are on page 1of 26

Ren Descartes (15961650) Ren Descartes is often credited with being the Father of Modern Philosophy.

This title is justified due both to his break with the traditional Scholastic-Aristotelian philosophy prevalent at his time and to his development and promotion of the new, mechanistic sciences. His fundamental break with Scholastic philosophy was twofold. First, Descartes thought that the Scholastics method was prone to doubt given their reliance on sensation as the source for all knowledge. Second, he wanted to replace their final causal model of scientific explanation with the more modern, mechanistic model. Descartes attempted to address the former issue via his method of doubt. His basic strategy was to consider false any belief that falls prey to even the slightest doubt. This hyperbolic doubt then serves to clear the way for what Descartes considers to be an unprejudiced search for the truth. This clearing of his previously held beliefs then puts him at an epistemological ground-zero. From here Descartes sets out to find something that lies beyond all doubt. He eventually discovers that I exist is impossible to doubt and is, therefore, absolutely certain. It is from this point that Descartes proceeds to demonstrate Gods existence and that God cannot be a deceiver. This, in turn, serves to fix the certainty of everything that is clearly and distinctly understood and provides the epistemological foundation Descartes set out to find. Once this conclusion is reached, Descartes can proceed to rebuild his system of previously dubious beliefs on this absolutely certain foundation. These beliefs, which are re-established with absolute certainty, include the existence of a world of bodies external to the mind, the dualistic distinction of the immaterial mind from the body, and his mechanistic model of physics based on the clear and distinct ideas of geometry. This points toward his second, major break with the Scholastic Aristotelian tradition in that Descartes intended to replace their system based on final causal explanations with his system based on mechanistic principles. Descartes also applied this mechanistic framework to the operation of plant, animal and human bodies, sensation and the passions. All of this eventually culminating in a moral system based on the notion of generosity. The presentation below provides an overview of Descartes philosophical thought as it relates to these various metaphysical, epistemological, religious, moral and scientific issues, covering the wide range of his published works and correspondence. 1. Life Ren Descartes was born to Joachim Descartes and Jeanne Brochard on March 31, 1596 in La Haye, France near Tours. He was the youngest of the couples three surviving children. The oldest child, Pierre, died soon after his birth on October 19, 1589. His sister, Jeanne, was probably born sometime the following year, while his surviving older brother, also named Pierre, was born on October 19, 1591. The Descartes clan was a bourgeois family composed of mostly doctors and some lawyers. Joachim Descartes fell into this latter category and spent most of his career as a member of the provincial

parliament. After the death of their mother, which occurred soon after Rens birth, the three Descartes children were sent to their maternal grandmother, Jeanne Sain, to be raised in La Haye and remained there even after their father remarried in 1600. Not much is known about his early childhood, but Ren is thought to have been a sickly and fragile child, so much so that when he was sent to board at the Jesuit college at La Fleche on Easter of 1607. There, Ren was not obligated to rise at 5:00am with the other boys for morning prayers but was allowed to rest until 10:00am mass. At La Fleche, Descartes completed the usual courses of study in grammar and rhetoric and the philosophical curriculum with courses in the verbal arts of grammar, rhetoric and dialectic (or logic) and the mathematical arts comprised of arithmetic, music, geometry and astronomy. The course of study was capped off with courses in metaphysics, natural philosophy and ethics. Descartes is known to have disdained the impractical subjects despite having an affinity for the mathematical curriculum. But, all things considered, he did receive a very broad liberal arts education before leaving La Fleche in 1614. Little is known of Descartes life from 1614-1618. But what is known is that during 1615-1616 he received a degree and a license in civil and canon law at the University of Poiters. However, some speculate that from 1614-1615 Descartes suffered a nervous breakdown in a house outside of Paris and that he lived in Paris from 1616-1618. The story picks up in the summer of 1618 when Descartes went to the Netherlands to become a volunteer for the army of Maurice of Nassau. It was during this time that he met Isaac Beekman, who was, perhaps, the most important influence on his early adulthood. It was Beekman who rekindled Descartes interest in science and opened his eyes to the possibility of applying mathematical techniques to other fields. As a New Years gift to Beekman, Descartes composed a treatise on music, which was then considered a branch of mathematics, entitled Compendium Musicae. In 1619 Descartes began serious work on mathematical and mechanical problems under Beekmans guidance and, finally, left the service of Maurice of Nassau, planning to travel through Germany to join the army of Maximilian of Bavaria. It is during this year (1619) that Descartes was stationed at Ulm and had three dreams that inspired him to seek a new method for scientific inquiry and to envisage a unified science. Soon afterwards, in 1620, he began looking for this new method, starting but never completing several works on method, including drafts of the first eleven rules of Rules for the Direction of the Mind. Descartes worked on and off on it for years until it was finally abandoned for good in 1628. During this time, he also worked on other, more scientifically oriented projects such as optics. In the course of these inquiries, it is possible that he discovered the law of refraction as early as 1626. It is also during this time that Descartes had regular contact with Father Marin Mersenne, who was to become his long time friend and contact with the intellectual community during his 20 years in the Netherlands. Descartes moved to the Netherlands in late 1628 and, despite several changes of address


Elizabeth was beginning, Descartes was already in the midst of writing a textbook version of his philosophy entitled Principles of Philosophy, which he ultimately dedicated to her. Although it was originally supposed to have six parts, he published it in 1644 with only four completed: The Principles of Human Knowledge, The Principles of Material Things, The Visible Universe, and The Earth. The other two parts were to be on plant and animal life and on human beings, but he decided it would be impossible for him to conduct all the experiments necessary for writing them. Elizabeth probed Descartes about issues that he had not dealt with in much detail before, including free will, the passions and morals. This eventually inspired Descartes to write a treatise entitled The Passions of the Soul, which was published just before his departure to Sweden in 1649. Also, during these later years, the Meditations and Principles were translated from Latin into French for a wider, more popular audience and were published in 1647. In late 1646, Queen Christina of Sweden initiated a correspondence with Descartes through a French diplomat and friend of Descartes named Chanut. Christina pressed Descartes on moral issues and a discussion of the absolute good. This correspondence eventually led to an invitation for Descartes to join the Queens court in Stockholm in February 1649. Although he had his reservations about going, Descartes finally accepted Christinas invitation in July of that year. He arrived in Sweden in September 1649 where he was asked to rise at 5:00am to meet the Queen to discuss philosophy, contrary to his usual habit, developed at La Fleche, of sleeping in late,. His decision to go to Sweden, however, was ill-fated, for Descartes caught pneumonia and died on February 11, 1650. 2. The Modern Turn a. Against Scholasticism Descartes is often called the Father of Modern Philosophy, implying that he provided the seed for a new philosophy that broke away from the old in important ways. This old philosophy is Aristotles as it was appropriated and interpreted throughout the later medieval period. In fact, Aristotelianism was so entrenched in the intellectual institutions of Descartes time that commentators argued that evidence for its the truth could be found in the Bible. Accordingly, if someone were to try to refute some main Aristotelian tenet, then he could be accused of holding a position contrary to the word of God and be punished. However, by Descartes time, many had come out in some way against one Scholastic-Aristotelian thesis or other. So, when Descartes argued for the implementation of his modern system of philosophy, breaks with the Scholastic tradition were not unprecedented. Descartes broke with this tradition in at least two fundamental ways. The first was his rejection of substantial forms as explanatory principles in physics. A substantial form was thought to be an immaterial principle of material organization that resulted in a particular thing of a certain kind. The main principle of substantial forms was the final cause or purpose of being that kind of thing. For example, the bird called the swallow. The substantial form of swallowness unites with matter so as to organize it for the sake of being a swallow kind of thing. This also means that any dispositions or faculties the




best skeptical arguments of his day But he was still not satisfied and decided to go a step further by considering false any belief that falls prey to even the slightest doubt. So, by the end of the First Meditation, Descartes finds himself in a whirlpool of false beliefs. However, it is important to realize that these doubts and the supposed falsehood of all his beliefs are for the sake of his method: he does not really believe that he is dreaming or is being deceived by an evil demon; he recognizes that his doubt is merely hyperbolic. But the point of this methodological or hyperbolic doubt is to clear the mind of preconceived opinions that might obscure the truth. The goal then is to find something that cannot be doubted even though an evil demon is deceiving him and even though he is dreaming. This first indubitable truth will then serve as an intuitively grasped metaphysical axiom from which absolutely certain knowledge can be deduced. For more, see Cartesian skepticism. 4. The Mind a. Cogito, ergo sum In the Second Meditation, Descartes tries to establish absolute certainty in his famous reasoning: Cogito, ergo sum or I think, therefore I am. These Meditations are conducted from the first person perspective, from Descartes. However, he expects his reader to meditate along with him to see how his conclusions were reached. This is especially important in the Second Meditation where the intuitively grasped truth of I exist occurs. So the discussion here of this truth will take place from the first person or I perspective. All sensory beliefs had been found doubtful in the previous meditation, and therefore all such beliefs are now considered false. This includes the belief that I have a body endowed with sense organs. But does the supposed falsehood of this belief mean that I do not exist? No, for if I convinced myself that my beliefs are false, then surely there must be an I that was convinced. Moreover, even if I am being deceived by an evil demon, I must exist in order to be deceived at all. So I must finally conclude that the proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind (AT VII 25: CSM II 16-17). This just means that the mere fact that I am thinking, regardless of whether or not what I am thinking is true or false, implies that there must be something engaged in that activity, namely an I. Hence, I exist is an indubitable and, therefore, absolutely certain belief that serves as an axiom from which other, absolutely certain truths can be deduced. b. The Nature of the Mind and its Ideas The Second Meditation continues with Descartes asking, What am I? After discarding the traditional Scholastic-Aristotelian concept of a human being as a rational animal due to the inherent difficulties of defining rational and animal, he finally concludes that he is a thinking thing, a mind: A thing that doubts, understands, affirms, denies, is willing, is unwilling, and also imagines and has sense perceptions (AT VII 28: CSM II 19). In the Principles, part I, sections 32 and 48, Descartes distinguishes intellectual perception and volition as what properly belongs to the nature of the mind alone while imagination and sensation are, in some sense, faculties of the mind insofar as it is united with a body. So imagination and sensation are faculties of the mind in a weaker sense

than intellect and will, since they require a body in order to perform their functions. Finally, in the Sixth Meditation, Descartes claims that the mind or I is a non-extended thing. Now, since extension is the nature of body, is a necessary feature of body, it follows that the mind is by its nature not a body but an immaterial thing. Therefore, what I am is an immaterial thinking thing with the faculties of intellect and will. It is also important to notice that the mind is a substance and the modes of a thinking substance are its ideas. For Descartes a substance is a thing requiring nothing else in order to exist. Strictly speaking, this applies only to God whose existence is his essence, but the term substance can be applied to creatures in a qualified sense. Minds are substances in that they require nothing except Gods concurrence, in order to exist. But ideas are modes or ways of thinking, and, therefore, modes are not substances, since they must be the ideas of some mind or other. So, ideas require, in addition to Gods concurrence, some created thinking substance in order to exist (see Principles of Philosophy, part I, sections 51 & 52). Hence the mind is an immaterial thinking substance, while its ideas are its modes or ways of thinking. Descartes continues on to distinguish three kinds of ideas at the beginning of the Third Meditation, namely those that are fabricated, adventitious, or innate. Fabricated ideas are mere inventions of the mind. Accordingly, the mind can control them so that they can be examined and set aside at will and their internal content can be changed. Adventitious ideas are sensations produced by some material thing existing externally to the mind. But, unlike fabrications, adventitious ideas cannot be examined and set aside at will nor can their internal content be manipulated by the mind. For example, no matter how hard one tries, if someone is standing next to a fire, she cannot help but feel the heat as heat. She cannot set aside the sensory idea of heat by merely willing it as we can do with our idea of Santa Claus, for example. She also cannot change its internal content so as to feel something other than heatsay, cold. Finally, innate ideas are placed in the mind by God at creation. These ideas can be examined and set aside at will but their internal content cannot be manipulated. Geometrical ideas are paradigm examples of innate ideas. For example, the idea of a triangle can be examined and set aside at will, but its internal content cannot be manipulated so as to cease being the idea of a three-sided figure. Other examples of innate ideas would be metaphysical principles like what is done cannot be undone, the idea of the mind, and the idea of God. Descartes idea of God will be discussed momentarily, but lets consider his claim that the mind is better known than the body. This is the main point of the wax example found in the Second Meditation. Here, Descartes pauses from his methodological doubt to examine a particular piece of wax fresh from the honeycomb: It has not yet quite lost the taste of the honey; it retains some of the scent of flowers from which it was gathered; its color shape and size are plain to see; it is hard, cold and can be handled without difficulty; if you rap it with your knuckle it makes a sound. (AT VII 30: CSM II 20) The point is that the senses perceive certain qualities of the wax like its hardness, smell,

and so forth. But, as it is moved closer to the fire, all of these sensible qualities change. Look: the residual taste is eliminated, the smell goes away, the color changes, the shape is lost, the size increases, it becomes liquid and hot (AT VII 30: CSM II 20). However, despite these changes in what the senses perceive of the wax, it is still judged to be the same wax now as before. To warrant this judgment, something that does not change must have been perceived in the wax. This reasoning establishes at least three important points. First, all sensation involves some sort of judgment, which is a mental mode. Accordingly, every sensation is, in some sense, a mental mode, and the more attributes [that is, modes] we discover in the same thing or substance, the clearer is our knowledge of that substance (AT VIIIA 8: CSM I 196). Based on this principle, the mind is better known than the body, because it has ideas about both extended and mental things and not just of extended things, and so it has discovered more modes in itself than in bodily substances. Second, this is also supposed to show that what is unchangeable in the wax is its extension in length, breadth and depth, which is not perceivable by the senses but by the mind alone. The shape and size of the wax are modes of this extension and can, therefore, change. But the extension constituting this wax remains the same and permits the judgment that the body with the modes existing in it after being moved by the fire is the same body as before even though all of its sensible qualities have changed. One final lesson is that Descartes is attempting to wean his reader from reliance on sense images as a source for, or an aid to, knowledge. Instead, people should become accustomed to thinking without images in order to clearly understand things not readily or accurately represented by them, for example, God and the mind. So, according to Descartes, immaterial, mental things are better known and, therefore, are better sources of knowledge than extended things. 5. God a. The Causal Arguments At the beginning of the Third Meditation only I exist and I am a thinking thing are beyond doubt and are, therefore, absolutely certain. From these intuitively grasped, absolutely certain truths, Descartes now goes on to deduce the existence of something other than himself, namely God. Descartes begins by considering what is necessary for something to be the adequate cause of its effect. This will be called the Causal Adequacy Principle and is expressed as follows: there must be at least as much reality in the efficient and total cause as in the effect of that cause, which in turn implies that something cannot come from nothing (AT VII 40: CSM II 28). Here Descartes is espousing a causal theory that implies whatever is possessed by an effect must have been given to it by its cause. For example, when a pot of water is heated to a boil, it must have received that heat from some cause that had at least that much heat. Moreover, something that is not hot enough cannot cause water to boil, because it does not have the requisite reality to bring about that effect. In other words, something cannot give what it does not have. Descartes goes on to apply this principle to the cause of his ideas. This version of the


supposed to be an absolutely certain intuition as well. b. The Ontological Argument The ontological argument is found in the Fifth Meditation and follows a more straightforwardly geometrical line of reasoning. Here Descartes argues that Gods existence is deducible from the idea of his nature just as the fact that the sum of the interior angles of a triangle are equal to two right angles is deducible from the idea of the nature of a triangle. The point is that this property is contained in the nature of a triangle, and so it is inseparable from that nature. Accordingly, the nature of a triangle without this property is unintelligible. Similarly, it is apparent that the idea of God is that of a supremely perfect being, that is, a being with all perfections to the highest degree. Moreover, actual existence is a perfection, at least insofar as most would agree that it is better to actually exist than not. Now, if the idea of God did not contain actual existence, then it would lack a perfection. Accordingly, it would no longer be the idea of a supremely perfect being but the idea of something with an imperfection, namely nonexistence, and, therefore, it would no longer be the idea of God. Hence, the idea of a supremely perfect being or God without existence is unintelligible. This means that existence is contained in the essence of an infinite substance, and therefore God must exist by his very nature. Indeed, any attempt to conceive of God as not existing would be like trying to conceive of a mountain without a valley it just cannot be done. 6. The Epistemological Foundation a. Absolute Certainty and the Cartesian Circle Recall that in the First Meditation Descartes supposed that an evil demon was deceiving him. So as long as this supposition remains in place, there is no hope of gaining any absolutely certain knowledge. But he was able to demonstrate Gods existence from intuitively grasped premises, thereby providing, a glimmer of hope of extricating himself from the evil demon scenario. The next step is to demonstrate that God cannot be a deceiver. At the beginning of the Fourth Meditation, Descartes claims that the will to deceive is undoubtedly evidence of malice or weakness so as to be an imperfection. But, since God has all perfections and no imperfections, it follows that God cannot be a deceiver. For to conceive of God with the will to deceive would be to conceive him to be both having no imperfections and having one imperfection, which is impossible; it would be like trying to conceive of a mountain without a valley. This conclusion, in addition to Gods existence, provides the absolutely certain foundation Descartes was seeking from the outset of the Meditations. It is absolutely certain because both conclusions (namely that God exists and that God cannot be a deceiver) have themselves been demonstrated from immediately grasped and absolutely certain intuitive truths. This means that God cannot be the cause of human error, since he did not create humans with a faculty for generating them, nor could God create some being, like an evil demon, who is bent on deception. Rather, humans are the cause of their own errors when they do not use their faculty of judgment correctly. Second, Gods non-deceiving nature also serves to guarantee the truth of all clear and distinct ideas. So God would be a deceiver, if

there were a clear and distinct idea that was false, since the mind cannot help but believe them to be true. Hence, clear and distinct ideas must be true on pain of contradiction. This also implies that knowledge of Gods existence is required for having any absolutely certain knowledge. Accordingly, atheists, who are ignorant of Gods existence, cannot have absolutely certain knowledge of any kind, including scientific knowledge. But this veridical guarantee gives rise to a serious problem within the Meditations, stemming from the claim that all clear and distinct ideas are ultimately guaranteed by Gods existence, which is not established until the Third Meditation. This means that those truths reached in the Second Meditation, such as I exist and I am a thinking thing, and those principles used in the Third Meditation to conclude that God exists, are not clearly and distinctly understood, and so they cannot be absolutely certain. Hence, since the premises of the argument for Gods existence are not absolutely certain, the conclusion that God exists cannot be certain either. This is what is known as the Cartesian Circle, because Descartes reasoning seems to go in a circle in that he needs Gods existence for the absolute certainty of the earlier truths and yet he needs the absolute certainty of these earlier truths to demonstrate Gods existence with absolute certainty. Descartes response to this concern is found in the Second Replies. There he argues that Gods veridical guarantee only pertains to the recollection of arguments and not the immediate awaRenss of an arguments clarity and distinctness currently under consideration. Hence, those truths reached before the demonstration of Gods existence are clear and distinct when they are being attended to but cannot be relied upon as absolutely certain when those arguments are recalled later on. But once Gods existence has been demonstrated, the recollection of the clear and distinct perception of the premises is sufficient for absolutely certain and, therefore, perfect knowledge of its conclusion (see also the Fifth Meditation at AT VII 69-70: CSM II XXX). b. How to Avoid Error In the Third Meditation, Descartes argues that only those ideas called judgments can, strictly speaking, be true or false, because it is only in making a judgment that the resemblance, conformity or correspondence of the idea to things themselves is affirmed or denied. So if one affirms that an idea corresponds to a thing itself when it really does not, then an error has occurred. This faculty of judging is described in more detail in the Fourth Meditation. Here judgment is described as a faculty of the mind resulting from the interaction of the faculties of intellect and will. Here Descartes observes that the intellect is finite in that humans do not know everything, and so their understanding of things is limited. But the will or faculty of choice is seemingly infinite in that it can be applied to just about anything whatsoever. The finitude of the intellect along with this seeming infinitude of the will is the source of human error. For errors arise when the will exceeds the understanding such that something laying beyond the limits of the understanding is voluntarily affirmed or denied. To put it more simply: people make mistakes when they choose to pass judgment on things they do not fully understand. So the will should be restrained within the bounds of what the mind understands in order to



he does not elaborate to Gassendi, Descartes does provide some insight in a 21 May 1643 letter to Elizabeth. In that letter, Descartes distinguishes between various primitive notions. The first is the notion of the body, which entails the notions of shape and motion. The second is the notion of the mind or soul, which includes the perceptions of the intellect and the inclinations of the will. The third is the notion of the union of the soul with the body, on which depend the notion of the souls power to move the body and the bodys power to cause sensations and passions in the soul. The notions entailed by or included in the primitive notions of body and soul just are the notions of their respective modes. This suggests that the notions depending on the primitive notion of the union of soul and body are the modes of the entity resulting from this union. This would also mean that a human being is one thing instead of two things that causally interact through contact and motion as Elizabeth and Gassendi supposed. Instead, a human being, that is, a soul united with a body, would be a whole that is more than the sum of its parts. Accordingly, the mind or soul is a part with its own capacity for modes of intellect and will; the body is a part with its own capacity for modes of size, shape, motion and quantity; and the union of mind and body or human being, has a capacity for its own set of modes over and above the capacities possessed by the parts alone. On this account, modes of voluntary bodily movement would not be modes of the body alone resulting from its mechanistic causal interaction with a mental substance, but rather they would be modes of the whole human being. The explanation of, for example, raising the arm would be found in a principle of choice internal to human nature and similarly sensations would be modes of the whole human being. Hence, the human being would be causing itself to move and would have sensations and, therefore, the problem of causal interaction between mind and body is avoided altogether. Finally, on the account sketched here, Descartes human being is actually one, whole thing, while mind and body are its parts that God could make exist independently of one another. However, a final point should be made before closing this section. The position sketched in the previous couple of paragraphs is not the prevalent view among scholars and requires more justification than can be provided here. Most scholars understand Descartes doctrine of the real distinction between mind and body in much the same way as Elizabeth and Gassendi did such that Descartes human being is believed to be not one, whole thing but two substances that somehow mechanistically interact. This also means that they find the mind-body problem to be a serious, if not fatal, flaw of Descartes entire philosophy. But the benefit of the brief account provided here is that it helps explain Descartes lack of concern for this issue and his persistent claims that an understanding of the union of mind and body would put to rest peoples concerns about causal interaction via contact and motion. 8. Body and the Physical Sciences a. Existence of the External World In the Sixth Meditation, Descartes recognizes that sensation is a passive faculty that receives sensory ideas from something else. But what is this something else?



From the simple fact that I consider two halves of a part of matter, however small it may be, as two complete substances . . . I conclude with certainty that they are really divisible. (AT III 477: CSMK 202-203 These considerations in general, and this quotation in particular, lead to another distinct feature of Cartesian body, namely that extension is infinitely divisible. The point is that no matter how small a piece of matter, it can always be divided in half, and then each half can itself be divided in half, and so on to infinity. These considerations about the vacuum and the infinite divisibility of extension amount to a rejection of atomism. Atomism is a school of thought going back to the ancients, which received a revival in the 17th century most notably in the philosophy and science of Pierre Gassendi. On this account, all change in the universe could be explained by the movements of very small, indivisible particles called atoms in a void or empty space. But, if Descartes arguments for rejecting the vacuum and the infinite divisibility of matter are sound, then atomism must be false, since the existence of indivisible atoms and an empty space would both be unintelligible. c. Physics Descartes devised a non-atomistic, mechanistic physics in which all physical phenomena were to be explain by the configuration and motion of a bodys miniscule parts. This mechanistic physics is also a point of fundamental difference between the Cartesian and Scholastic-Aristotelian schools of thought. For the latter (as Descartes understood them), the regular behavior of inanimate bodies was explained by certain ends towards which those bodies strive. Descartes, on the other hand, thought human effort is better directed toward the discovery of the mechanistic causes of things given the uselessness of final causal explanations and how it is vain to seek Gods purposes. Furthermore, Descartes maintained that the geometric method should also be applied to physics so that results are deduced from the clear and distinct perceptions of the geometrical or quantifiable properties found in bodies, that is, size, shape, motion, determination (or direction), quantity, and so forth. Perhaps the most concise summary of Descartes general view of the physical universe is found in part III, section 46 of the Principles: From what has already been said we have established that all the bodies in the universe are composed of one and the same matter, which is divisible into indefinitely many parts, and is in fact divided into a large number of parts which move in different directions and have a sort of circular motion; moreover, the same quantity of motion is always preserved in the universe. (AT VIIIA 100: CSM I 256) Since the matter constituting the physical universe and its divisibility were previously discussed, a brief explanation of the circular motion of bodies and the preservation of motion is in order. The first thesis is derived from Gods immutability and implies that no quantity of motion is ever added to or subtracted from the universe, but rather quantities of motion are merely passed from one body to another. Gods immutability is also used to support the first law of motion, which is that each and everything, in so far as it can, always continues in the same state; and thus what is once in motion always continues in

motion (AT VIIIA 62-63: CSM I 241). This principle indicates that something will remain in a given state as long as it is not being affected by some external cause. So a body moving at a certain speed will continue to move at that speed indefinitely unless something comes along to change it. The second thesis about the circular motion of bodies is discussed at Principles, part II, section 33. This claim is based on the earlier thesis that the physical universe is a plenum of contiguous bodies. On this account, one moving body must collide with and replace another body, which, in turn, is set in motion and collides with another body, replacing it and so on. But, at the end of this series of collisions and replacements, the last body moved must then collide with and replace the first body in the sequence. To illustrate: suppose that body A collides with and replaces body B, B replaces C, C replaces D, and then D replaces A. This is known as a Cartesian vortex. Descartes second law of motion is that all motion is in itself rectilinear; and hence any body moving in a circle always tends to move away from the center of the circle which it describes (AT VIIIA 63-64: CSM I 241-242). This is justified by Gods immutability and simplicity in that he will preserve a quantity of motion in the exact form in which it is occurring until some created things comes along to change it. The principle expressed here is that any body considered all by itself tends to move in a straight line unless it collides with another body, which deflects it. Notice that this is a thesis about any body left all by itself, and so only lone bodies will continue to move in a straight line. However, since the physical world is a plenum, bodies are not all by themselves but constantly colliding with one another, which gives rise to Cartesian vortices as explained above. The third general law of motion, in turn, governs the collision and deflection of bodies in motion. This third law is that if a body collides with another body that is stronger than itself, it loses none of its motion; but if it collides with a weaker body, it loses a quantity of motion (AT VIIIA 65: CSM I 242). This law expresses the principle that if a bodys movement in a straight line is less resistant than a stronger body with which it collides, then it wont lose any of its motion but its direction will be changed. But if the body collides with a weaker body, then the first body loses a quantity of motion equal to that given in the second. Notice that all three of these principles doe not employ the goals or purposes (that is, final causes) utilized in Scholastic-Aristotelian physics as Descartes understood it but only the most general laws of the mechanisms of bodies by means of their contact and motion. d. Animal and Human Bodies In part five of the Discourse on Method, Descartes examines the nature of animals and how they are to be distinguished from human beings. Here Descartes argues that if a machine were made with the outward appearance of some animal lacking reason, like a monkey, it would be indistinguishable from a real specimen of that animal found in nature. But if such a machine of a human being were made, it would be readily distinguishable from a real human being due to its inability to use language. Descartes point is that the use of language is a sign of rationality and only things endowed with

minds or souls are rational. Hence, it follows that no animal has an immaterial mind or soul. For Descartes this also means that animals do not, strictly speaking, have sensations like hunger, thirst and pain. Rather, squeals of pain, for instance, are mere mechanical reactions to external stimuli without any sensation of pain. In other words, hitting a dog with a stick, for example, is a kind of input and the squeal that follows would be merely output, but the dog did not feel anything at all and could not feel pain unless it was endowed with a mind. Humans, however, are endowed with minds or rational souls, and therefore they can use language and feel sensations like hunger, thirst, and pain. Indeed, this Cartesian fact is at the heart of Descartes argument for the union of the mind with the body summarized near the end of part five of the Discourseand laid out in full in the Sixth Meditation. Yet Descartes still admits that both animal and human bodies can be best understood to be machine[s] made of earth, which God forms. (AT XI 120: CSM I 99). The point is that just as the workings of a clock can be best understood by means of the configuration and motion of its parts so also with animal and human bodies. Indeed, the heart of an animal and that of a human being are so much alike that he advises the reader unversed in anatomy to have the heart of some large animal with lungs dissected before him (for such a heart is in all respects sufficiently like that of a man), and be shown the two chambers or cavities which are present in it (AT VI 47: CSM I 134). He then goes on to describe in some detail the motion of the blood through the heart in order to explain that when the heart hardens it is not contracting but really swelling in such a way as to allow more blood into a given cavity. Although this account goes contrary to the (more correct) observation made by William Harvey, an Englishman who published a book on the circulation of the blood in 1628, Descartes argues that his explanation has the force of geometrical demonstration. Accordingly, the physiology and biology of human bodies, considered without regard for those functions requiring the soul to operate, should be conducted in the same way as the physiology and biology of animal bodies, namely via the application of the geometrical method to the configuration and motion of parts. 9. Sensations and Passions In his last published work, Passions of the Soul, Descartes provides accounts of how various motions in the body cause sensations and passions to arise in the soul. He begins by making several observations about the mind-body relation. The whole mind is in the whole body and the whole in each of its parts but yet its primary seat is in a little gland at the center of the brain now known as the pineal gland. Descartes is not explicit about what he means by the whole mind in the whole body and the whole in each of its parts. But this was not an uncommon way of characterizing how the soul is united to the body at Descartes time. The main point was that the soul makes a human body truly human; that is, makes it a living human body and not merely a corpse. Given Descartes unexplained use of this phrase, it is reasonable to suppose that he used it in the way his contemporaries would have understood it. So the mind is united to the whole body and the whole in each of its parts insofar as it is a soul or principle of life. Accordingly, the bodys union with the soul makes it a living human body or a human body, strictly speaking (see letter to Mersenne dated 9 February 1645). But, the primary seat, that is,



health when ill nor freedom when imprisoned. It is difficult to see why the fourth maxim is included. Indeed, Descartes himself seems hesitant about including it when he states at the outset that his provisional moral code consists of three or four maxims. Although he does not examine other occupations, Descartes is content with his current work because of the pleasure he receives from discovering new and not widely known truths. This seems to imply the correct choice of occupation can ensure a degree of contentedness that could not be otherwise achieved if one is engaged in an occupation for which one is not suited. Descartes also claims that his current occupation is the basis of the other three maxims, because it is his current plan to continue his instruction that gave rise to them. He concludes with a brief discussion of how his occupational path leads to the acquisition of knowledge, which, in turn, will lead to all the true goods within his grasp. His final point is that learning how best to judge what is good and bad makes it possible to act well and achieve all attainable virtues and goods. Happiness is assured when this point is reached with certainty. b. Generosity After the Discourse of 1637, Descartes did not take up the issue of morality in any significant way again until his correspondence with Princess Elizabeth in 1643, which culminated in his remarks about generosity in part 3 of the Passions of the Soul. Given the temporal distance between his main reflections on morality, it is easy to attribute to Descartes two moral systems the provisional moral code and the ethics of generosity. But Descartes later moral thinking retains versions of the second and third maxim without much mention of the first and fourth. This indicates that Descartes later moral theory is really an extension of his earlier thought with the second and third maxims at its core. At Passions, part 3, section 153, Descartes claims that the virtue of generosity causes a persons self-esteem to be as great as it may legitimately be and has two components. First is knowing that only the freedom to dispose volitions is in anyones power. Accordingly, people should only be praised or blamed for using ones freedom either well or poorly. The second component is the feeling of a firm and constant resolution to use ones freedom well such that one can never lack the will to carry out whatever has been judged to be best. Notice that both components of generosity relate to the second and third maxim of the earlier provisional moral code. The first component is reminiscent of the third maxim in its acknowledgment of peoples freedom of choice and the control they have over the disposition of their will or desire, and therefore they should be praised and blamed only for those things that are within their grasp. The second component relates to the second maxim in that both pertain to firm and resolute action. Generosity requires a resolute conviction to use free will correctly, while the second maxim is a resolution to stick to the judgment most likely to lead to a good action absent a significant reason for changing course. However, a difference between these two moral codes is that the provisional moral code of the Discourse focuses on the correct use and resolute enactment of probable judgments, while the later ethics of generosity emphasizes a firm resolution to use free will correctly. Hence, in both moral systems, the correct use of mental faculties,

namely judgment and free will, and the resolute pursuit of what is judged to be good is to be enacted. This, in turn, should lead us to a true state of generosity so as to legitimately esteem ourselves as having correctly used those faculties through which humans are most in the likeness of God. 11. References and Further Reading a. Primary Sources Descartes, Ren, Oeuvres de Descartes, eds. Charles Adam and Paul Tannery, Paris: Vrin, originally published 1987-1913. This is still the standard edition of all of Descartes works and correspondence in their original languages. Cited in the text as AT volume, page. Descartes, Ren, The Philosophical Writings of Descartes, trans. John Cottingham, Robert Stoothoff, Dugald Murdoch and Anthony Kenny, Cambridge: Cambridge Universiety Press, 3 vols.1984-1991. This is the standard English translation of Descartes philosophical works and correspondence. Cited in the text as CSM or CSMK volume, page. b. Secondary Sources Ariew, Roger, Marjorie GRen, eds., Descartes and His Contemporaries: Meditations, Objections, and Replies, Chicago: University of Chicago Press, 1995. This is a collection of essays by prominent scholars about various issues raised in the Meditations, objections to them and the adequacy or inadequacy of Descartes replies. Broughton, Janet, Descartess Method of Doubt, Princeton: Princeton University Press, 2003. A study of Descartes method and its results. Dicker, Georges, Descartes: An Analytical and Historical Introduction, Oxford: Oxford University Press, 1993. A clear and concise introduction to Descartes philosophy. Frankfurt, Harry, Demons, Dreamers and Madmen: the Defense of Reason in Descartes Meditations, Indianapolis: Bobbs-Merrill, 1970. A classic examination of Descartes Meditations. Garber, Daniel, Descartes Metaphysical Physics, Chicago and London: University of Chicago Press, 1992. Provides a detailed account of Cartesian science and its metaphysical foundations. Gaukroger, Stephen, Descartes: An Intellectual Biography, Oxford: Clarendon Press, 1995. Though somewhat technical, this is a very good biography of Descartes intellectual development emphasizing his early years and his interests in mathematics and science. Kenny, Anthony, Descartes: A Study of His Philosophy, New York: Random House, 1968.

A classic study of Descartes philosophy through the Meditations. Marshall, John, Descartess Moral Theory, Ithaca and London: Cornell University Press, 1998. One of the few book length explications of Descartes moral theory. Rodis-Lewis, Genevieve, Descartes: His Life and Thought, trans. Jane Marie Todd, Ithaca and London: Cornell University Press, 1998 This is a very readable and enjoyable biography. Rozemond, Marleen, Descartess Dualism, Cambridge: Harvard University Press, 1998. Provides an interpretation of the real distinction between mind and body, their causal interaction and theory of sensation within the context of late Scholastic theories of soul-body union and sensation. Secada, Jorge, Cartesian Metaphysics: The Late Scholastic Origins of Modern Philosophy, Cambridge: Cambridge University Press, 2000. An at times technical, though readable, account of the whole of Descartes metaphysics from within the context of late Scholasticism. Skirry, Justin, Descartes and the Metaphysics of Human Nature, London: Thoemmes-Continuum Press, 2005. Provides an account of Descartes theory of mind-body union and how it helps him to avoid the mind-body problem. Verbeek, Theo, Descartes and the Dutch: Early Reactions to Cartesian Philosophy 1637-1650,Carbondale: Southern Illinois University Press, 1994. Provides a history and account of the controversies at Utrecht and Leiden. Williston, Byron and Andre Gomby, eds., Passion and Virtue in Descartes, New York: Humanity Books, 2003. An anthology of essays by many noted scholars on Descartes theory of the passions and aspects of his later moral theory. Williams, Bernard, Descartes: The Project of Pure Enquiry, Sussex: Harvester Press, 1978. Classic account of Descartes philosophy in general. Wilson, Margaret, Descartes, London and Boston: Routledge and Kegan Paul, 1978. A classic in Descartes scholarship covering the whole of his philosophy as expressed in the Meditations.