Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 1 The Mind and Body Relationship in the Cartesian System of Knowledge and its Possible Derivation into Monism Françoise Monnoyeur Centre Jean Pepin, CNRS, 94801 Villejuif Cedex, Paris, France e-mail: fmonnoy@hotmail.com In their book on Descartes's changing mind, Peter Machamer and J.E. McGuire argue that Descartes discarded dualism to embrace a kind of monism. It is intriguing to investigate if the master of dualism could have changed his mind about the central aspect of his system. After reviewing the position of the authors, we will consider how and in what terms Descartes did not go back on his favorite doctrine but may have fooled himself about the nature of his dualism. It is my contention that the so-called problematic Cartesian dualism has its origin in the lack of proper definition of mind and body as substances and the role of their respective attributes, thought and extension in the definition of the substances. The main answer to Machamer and McGuire's thesis is that Descartes could develop his epistemology of mind and body independently of a metaphysics of substance and its attributes. In other words not only did Descartes not change his mind, but he persevered and enriched his dualist metaphysics. The subsidiary answer to the authors is that the concessions given by Descartes to the opponents of his dualism can be found in earlier works, but, pace the authors, they did not cause him not to develop his dualism in the first place. KEYWORDS: Descartes; substance; mind and body union; dualism; monism; spiritual and material substance; main attributes; extension; thought; Gassendi; Henry More. Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 2 1. INTRODUCTION The last sentence of the authors of Descartes's changing mind is the following: "Perhaps, at the end of his life, Descartes was not much a dualist after all." (Machamer and McGuire 2009: 241). The statement suggests that Descartes in his final works gave up his dualism between the strict separation between mind and body, and embraced a monist position. According to Machamer and McGuire, for the late Descartes mind and body have certain attributes in common and can no longer be considered as independent substances. They claim that although such an idea is out of context in the works of the young Descartes, he developed it gradually in his later writings. The question of whether Descartes changed his mind on the nature of these substances and their union is of prime importance. This problem is a sensitive one because most of Descartes's opponents, such as Gassendi, Leibniz, or Henry More, emphasized that Descartes's conception was incoherent, a failure, or at least incomplete. Nevertheless, contemporary commentators such as Lili Allanen, Ted Richardson or Tad Schmaltz have tried to make sense of it. After reading Descartes's changing mind, it seems to me that a new attempt to save the coherence of the mind/body union emerges, a union without dualism and an epistemology free of the metaphysics of substance. In his late correspondence with Henry More, Descartes amended his theory that mind and body were incommensurable substances. Is this enough to consider that Descartes had really abandoned his dualism? How do the authors reason to reach this position? They invite us to revisit the Cartesian mind-body union problem and describe a developmental process of knowledge at work in Descartes's philosophy. To back up their enterprise, Machamer and Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 3 McGuire quote the following remarkable passage of a reply from Descartes to Henry More of February 5, 1649: "True, our mind is not the measure of reality or truth; but certainly it should be the measure of what we affirm or deny. What is more rash or absurd than to want to make judgments about matters which we admit our mind cannot perceive?" (Letter to More, February 5, 1649). (Machamer and McGuire 2009: 241). Descartes acknowledges here a discrepancy between the nature of reality and what of it the mind can reach. While reality or truth is not entirely perceived by the mind, it still may be possible for us to glimpse it momentarily. This statement seems to be very much in retreat of the conclusions we could have drawn from the reading of the Meditations or the Discourse on the Method. Descartes's acceptance of our limited knowledge leads the authors to believe that Descartes changed his mind about his dualism in his later correspondence, the Passions of the Soul and Principles of Philosophy. In order to answer this claim, we will revisit the Cartesian process of knowledge according to Machamer and McGuire's book. We shall argue that Descartes did not really change his mind, even if he was not married to a strict dualism (finding evidence for this in the correspondence) nor truly based his dualism on solid foundation of theory of substance. We shall investigate this last point and envision how the problem of the mind/body union is directly related to the conception of substance and its attributes. Finally, after reviewing Descartes's early correspondence with Gassendi, and late correspondence with Henry More, we will consider that, although Descartes may have been sensitive to some of their objections, he did not reconsider his dualist position. Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 4 2. HOW, ACCORDING TO MACHAMER AND McGUIRE, DESCARTES BECAME A KIND OF MONIST Whereas many philosophers have recognized the inconsistencies of Cartesian dualism, Peter Machamer and J.E. McGuire describe an epistemological teleology capable of resolving these metaphysical discrepancies. Tracing the development of Descartes's views on mind and body, they reached the conclusion that Descartes became gradually less sure he could fully understand the nature of substances. They find that Descartes had come to realize the limitations of the human mind and therefore the impossibility of justifying its absolute distinction from the body. A. Machamer and McGuire emphasize that for Descartes, human knowledge is limited and that only God has absolute knowledge. Machamer and McGuire announce in their first chapter: "We will argue that Descartes's dualism has to be understood in terms of what we call his epistemic teleology" (Machamer and McGuire 2009: 4) They articulate their reasoning in the framework of a developmental epistemology according to which Descartes would have, in the first part of the Principles and then in the Passions of the Soul, given up his dualism because of the impossibility of knowing the nature of substances. According to Descartes, our mind presents us with two separate substances, mind and body with distinct attributes of thought and extension (Principles of Philosophy). According to Machamer and McGuire, because of the limitation of our intellect, we cannot have insight about the nature of spiritual substance or material substance. Descartes gave up his desire for absolute knowledge and instead organized his epistemology according to the limits of our mind. For instance, the authors interpret principle 62, first part of the Principles in these terms: "Descartes now emphasizes what we may know, namely, the attributes of extension and thought, rather than substance itself." (Machamer and McGuire 2009: 227). Here Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 5 begins for them the epistemological stance taken by Descartes to underline that only the attributes are knowable. Their interpretation does not hold in regards to what Descartes wrote about thought and extension in the following Principle 64, I: "Because when we regard them (thought and extension) as in the substances of which they are modes, we distinguish them from these substances and take them for what they actually are; while, on the contrary, if we wish to consider them apart from the substances in which they are, that will have the effect of our taking them as self-subsisting things and thus confounding the ideas of mode and substance." (Descartes 2000: 249). Descartes insists here that we would confuse attributes and substance if we separate attributes from their respective substances. The authors emphasize that Descartes turned his back progressively on ontology and adopted a more pragmatic attitude towards knowledge that they call "epistemic teleology shift." They write: "The epistemic consequence of this, as we hope to show, is that the world may contain many things that we neither know nor have the possibility of knowing. More specifically it means, for example, that we cannot know, or minimally we cannot know that we know, the real nature of substances, but only some of their useful attributes or particular modes that, yet, are, still mind-independent." (Machamer and McGuire 2009: 2). In principle 3 of Part II, Descartes contradicts this statement: "Sensory perceptions do not teach us what is really in things, but merely what is useful or harmful to man's composite nature." (Descartes 2000: 254) Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 6 Machamer and McGuire argue from Descartes recognition of the limits of human knowledge as regards the divine to the limitation of human knowledge about the nature of substances; they write: "Descartes came to see more clearly that just as God's transcendent nature is beyond our comprehension, so likewise, there is much in created reality that surpasses our cognitive grasp since it lies beyond the limitations of the finite intellect." (Machamer and McGuire 2009: 197). For Machamer and McGuire, if it is true that God is the warrant of our knowledge and that mind alone defines of material substance as geometric extension (Principles of Philosophy, II), it is sensation with mind that shapes the interaction between mind and body. They emphasize that sensation is rooted in our body and our best ally to ease our life while the mind alone is not able to guide us. Nevertheless, we cannot deny that how clearly this inter-substance relation can be expressed depends on the mind. By his own criteria, Descartes would have to provide a clear and distinct idea of how this interaction takes place. The Cartesian epistemological shift, as described by the authors, tends to identify the nature of the mind with the one of the body and this should become more obvious in Descartes's mature period. B. For Machamer and McGuire, union between mind and body concerns us as persons and excludes metaphysics. The idea of a person is linked to the idea of a soul and a body. The authors point out that, at the time of his later works, The Passions of the Soul and the Principles, Descartes relies on sensation to reveal the union between mind and body. They write in Descartes's changing mind: "In his treatment of mind-body distinction as a substantial union constitutive of the nature of person, he begins to downplay any need for maintaining a strict and direct Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 7 ontological distinction between mind and body.... But notice that is sensations that reveal immediately that the union is real and substantial." (Machamer and McGuire 2009: 233234). The authors recall that the union of mind and body takes place in a person and may want to say that there are different laws in the metaphysical and physical relationship between matter and mind. To clarify how the union between mind and body should be viewed, the authors argue from the Passions of the Soul that we should consider the person instead of the body and the mind and write: "But if the principal attributes of soul and body (thinking and extension) can be both active and passive, and if we know a substance only through its principal attributes, or are able to distinguish soul and body solely by means of their principle attribute, it seems on this basis alone that we will be unable to make and infer a real mind/body distinction."(Machamer and McGuire 2009: 239). Thus mind is identified with the soul, which happens in the process of relying on our own experience. In everyday life, we may experience something of soul/body union, and therefore acquire a kind of knowledge. For the authors, the Passions of the Soul give us a clue to the indescribable union that seemingly displaces both substances. C. According to Machamer and McGuire, mind and body do not need to exist as substances The authors show how the epistemology in the Principles of Part II concerns our limited and viable knowledge rather than metaphysics. As Descartes identifies spiritual substance with thinking, and material substance with extension, the authors contend that Descartes no longer requires any substance in relation to mind and body. According to the authors, the fact that Descartes admits that we cannot know the totality of the world created by God proves our Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 8 human limitation and the impossibility of knowing what substances are in themselves. In chapter six, the authors draw a conclusion on the attributes of Cartesian substances: "So there is no direct warrant for a real distinction, since these substances are not known by us directly but only through their principal attributes." (Machamer and McGuire 2009: 229). Regarding the separation of the substances, our mind presents us with distinct attributes of mind and body, that is to say thought and extension, but does not give us access to their intrinsic substances. They explain that we cannot have insight into the nature of spiritual substance or material substance because of the limited human intellect. Therefore, I would argue that this thesis in Descartes's changing mind is not defensible because it negates the fundamental role of thinking and corporeal substance. In their attempt to suppress the Cartesian theory of substance, the authors oppose the philosophers who locate the secret of the union within the substance: "In our view, the dispute between the dualists, the interactionists, and the trialists is misconceived because all parties treat the concepts of mind and body as requiring direct ontological reference. They also assume that Descartes is concerned from first to last with upholding, always in the same way, a real distinction between mind and body." (Machamer and McGuire 2009: 232). From here, it is clear that the authors oppose the dualists and trialists, and consider that the notion of substance has no role to play in Descartes's epistemology at the stage of the Principles, and is not needed to understand the union between mind and body. However, Descartes devotes most of the first part of his Principles to defining substance, namely the material in opposition to the spiritual substances, and these definitions are the building blocks of his philosophy. For Machamer and McGuire Descartes is already skeptical about these definitions in the first part Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 9 of this Principles. We shall consider in the next section how the definition of substance supports the concepts of mind and body union. 3. CARTESIAN DEFINITION OF SUBSTANCE AND WHY SUBSTANCE CANNOT BE IGNORED A. Substance and dualism The concept of substance is the ontological bedrock of the Cartesian system. As in most rationalist systems, substance justifies other conceptual distinctions and must therefore be understood with the utmost clarity. For Descartes, the definition of substance is what ultimately articulates his theory of the idea of God, matter, body, mind and person. That is to say that the Cartesian dualism is embedded in the notion of substance, and that if mind-substance and bodysubstance is discarded, so is his dualism. Marleen Rozemond, in her book Descartes's dualism, develops the same idea but not for the same reason; she writes: "It is certainly true that Descartes was concerned with the possibility of mind existing without body, but I will argue that this idea is not central to his argument. His dualism does not consist in this possibility, nor is it fundamental to the argument. Instead, crucial argument is Descartes's conception of substance, including important claims about the relationship between the nature or essence of a substance and the properties it can have." (Rozemond 2002: 1). Rozemond and I agree that substance and its attributes is at the center of the Cartesian dualism. While Rozemond is sure that Descartes develops with full clarity his conception of the two separate substances in order to make work his mechanism, it seems to me that Descartes's dualism articulates with difficulties the relation of the spiritual substance identified with the mind to the material substance, identified with the body. A sign of this difficult articulation is Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 10 the multiplication of interpretations concerning the number of substances involved. For instance, the trialists would argue that the mind/body in a person forms a third substance. In his attack against trialists, Dan Kaufman emphasizes that thought and extension are attributes of a different kind: "The fact that human beings have only the two principal attributes of thought and extension, in conjunction with the fact that all modes are modes of a principal attribute, shows that human beings must be only modes of thought and of extension." (Kaufman 2008: 71). This standpoint respects the Cartesian hierarchical ontology between substance, attribute and mode (way of being of attributes), and corroborates the dualist nature of the Cartesian substances mind and body. Machamer and McGuire do not acknowledge dualism, trialism or even monism because the notion of substance has for them no function in the Cartesian mind/body union. Instead of metaphysics of substance, the authors dwell on perceptual experience to understand the mind/body relation and write: "The system is comprised of two dependent created substances, mind and body, that are related in the closest way possible, by a shared identity of representative content brought about intentionality." (Machamer and McGuire 2009: 220). For them, these two dependent created substances, that is to say mind and body, do not even differ anymore from each other We can see how Machamer and McGuire progressively ruined all the basis of the Cartesian dualism. If Descartes had to be a monist, then mind and body should be two aspects of the same substance. So in order to form an opinion about Descartes's dualism or monism, we need to analyze the role of substance in the mind and body. The authors have considered that for Descartes substance does not play a role, explaining that progressively Descartes gave up any pretention to reach metaphysical conclusions. They mean that Descartes, aware of his cognitive Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 11 limits, would have preferred to abandon his dualism of substances; the authors explain: "Our point is that for epistemic purposes we are able to conceive substances only under their principal attributes or under their respective modes." (Machamer and McGuire 2009: 231). It seems to me, on the contrary, that for metaphysical and epistemic reasons, Descartes needs the concept of substance and that the principal attributes cannot replace the substances mind and body. In his article about Descartes's dualism, Gonzalo Rodriguez-Pereyra (2008) considers somewhat like Machamer and McGuire that thought and extension can replace substances; not because our knowledge of substance is limited as Machamer and McGuire claim, but because there would be only a conceptual and not a real difference between the nature of substance and its main attributes. That's why we need to investigate Descartes account of substance and its main attributes. In the first Part of the Principles, Descartes mentions three distinct substances: God, mind and matter and relates as such the two last substances to their attributes in P I, 64: "We then distinguish them (thought and extension) modally from substance, and they may be understood not less clearly and distinctly, provided that we do not think of them as substances or things separate from others, but simply as modes of things." (Descartes, 2000: 249). So Descartes underlines that modes should not be confused with the substances; this means that thought and extension should not be confused with mind and body as modes are just ways to be for the two substances. For instance, the modes of the corporeal substance are extension, shape, size. B. The relationship between substances and their attributes Substances and attributes have a special interaction within Cartesian dualism because on the one hand substances are stated to be independent from their attributes, and on the other hand they depend on their attributes to be detected by us as existence. The main thesis of the Cartesian Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 12 substance is the following: the first substance is divine, infinite and creates the other substances, spiritual and material substances. Each of these two substances has the following characteristics: they are created by God and persist by themselves in time, they have attributes that are proof of their own existence, and finally, they are subjects. In P I, 52 Descartes writes: "Created substances, however, whether corporeal or thinking, may be understood under this common concept: for they are things that need only the concurrence of God in order to exist. But yet substance cannot be first discovered merely from the fact that it is an existing thing, for that fact alone is not observed by us." (Descartes, 2000: 244.) Body and mind as substances need the concurrence of God to exist and their respective attributes depend on the existence of the substances body and soul. The other thesis is that substances need attributes to be known distinctly. Previously, in the appendix following his Responses to the Fifth Objections made by Gassendi, Descartes had mentioned, also, that substance is perceived through its attributes in the following terms: 'In distinguishing a substance from its accidents, we must consider both one and the other, and this helps greatly in coming to know it; whereas if instead we only separate by abstraction this substance from its accidents, that is, if we consider it quite alone without thinking of them, that prevents us from knowing it well, because it is by its accidents that the nature of substance is manifested." (Descartes, Cottingham et al. 1984a: 277) Also, in the first part of his Principles, Pl, 52, Descartes completes his definition of substance by admitting it is discovered through its attributes and quotes: Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 13 "We may, however, easily discover it (substance) by means of any one of its attributes, because it is a common notion that nothing is possessed of no attributes, properties, or qualities." (Descartes 2000: 244). Descartes admits here that the existence of substance is only detectable by its perceived attributes, as we do not have direct access to substance itself. Its attributes are, in fact, for us the manifestation of the existence of substance. Clear and distinct perception of attributes are representations of substance. This point is crucial for understanding the nature of Cartesian dualism, and consequently the power of the mind to discover that thought and extension reveal the existence of the spiritual and material substance. But as shown before, the attributes cannot exist alone, and at no time can be dissociated from substance as Machamer and McGuire believe. The question is then to understand the role of attributes in the definition of substance. First, it could be the source of confusion regarding the actual role or nature of substance in the Cartesian system. Second, as advocated by Machamer and McGuire, it could indicate Descartes's limitations in formulating an idea of metaphysical substance. Third, it could refer to the need to distinguish common experience of mind and body through their attributes from their metaphysical knowledge as spiritual and material substances. As Descartes never wrote that substance cannot be grasped totally, and even if he did not clarify if substance could be of different kind in the mind, body or union, his dualism cannot be discarded. As defined in the Principles of Philosophy, mind and body are two independent substances, but at the same time need to be perceived by extension and thought in order to be discovered as substances. The attributes function as the means of perception of an otherwise imperceptible entity, even in the case of the body. The Cartesian framework should then disclose the reason for inferring the existence of these two separate substances based on the perception of their attributes. In order to look into Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 14 this question we shall examine the definitions given by Descartes of mind and body as substances. One special character shared by the substances mind and body is to be subject of their attributes. In definition 7 following the Reply to the Second Set of Objections, Descartes emphasizes that substances do not much weight to the subject in relation to the individualization of the corporeal substance, and writes: "That substance which is the immediate subject of local extension and of the accidents that presuppose extension, such as shape, position, movement from place, and so on, is called body." (Descartes 2000: 162). For Rozemond (2002), the fact that substances are subjects is the proof they cannot be considered as the same entities. However what Descartes means with the "body" as 'immediate subject of extension' is not so clear. According to this definition, the role of corporeal substance is to be a subject of the main attribute extension. The subject seems then to be limited to support extension and does not have any other function in the corporeal substance itself. We conclude from this set of definitions that mind and body are not defined as substances as univocally as they could, and in consequence come short as independent subjects. The two substances mind and body exist for us because we can know something about their attributes. We are forced to concede that the nature of the substances relying on their attributes does puzzle our understanding of substance itself as much as Descartes may have been puzzled (Monnoyeur 1992). However, it seems difficult, as Machamer and McGuire do, to abandon dualism of substances even when these substances are discovered only through their respective attributes (thought for the mind and extension for the body). Substance and attributes are mutually dependent, and definition of mind and body is possible thanks to their respective main attribute thought and extension. Nevertheless, in no way these attributes can replace their substance and exist by themselves as Machamer and McGuire support it. Although Gonzalo RodriguezFinal Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 15 Pereyra considers like Machamer and McGuire that substance and main attributes are not distinct entities, he states that there is a dualism of properties at work. It seems to me that there is no identification between spiritual substance and thought on the one side, and corporeal substance and extension on the other side. In doing so, Descartes may perplex his readers and writes in Principle I, 53 of the first part of the Principles, AT IX-2, Volume 48 GF p 123: "Namely, extension in length, width and depth constitutes the nature of corporal substance." (Descartes, 2000: 244). and just after admitting in principle 9, Principles of Philosophy II, "Corporeal substance, when distinguished from its quantity, is confusedly conceived as something incorporeal..." (Descartes 2000: 256). Does Descartes mean here that corporeal substance could be incorporeal in its nature if it is conceived only as subject, and not as extension? As we can only conceive clearly extension, Descartes defines the nature of corporeal substance as extension, because as subject it would be confused. At this stage, we are very far from Stephen Gaukroger's statement about the nature of substance in Descartes's system of Natural Philosophy: "The first is that mind and body are separate substances with completely different sets of properties. One thing this means is that there is no grey area between the two, there are no blurred boundaries." (Gaukroger 2002: 92). My thesis is that there are two major conclusions about the relation of substance and its attributes; the first one is that extension and thought make us discover the existence of substance; the second one, is that although Descartes distinguishes the substance of mind from thought, and substance of the body from extension, his nature of his dualism is borne by the main attributes. Nevertheless, this does not mean that mind and body are the same substances, Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 16 in other words supported by a monist theory of substance. This double line of interpretation is interesting because it shows that Descartes wants to keep the metaphysics of substance separated from the perception of substance by its attributes, and that the dualism relies mainly on the attributes. Blake Dutton held that the conceptual weakness of the Cartesian dualism comes from the absence of a justified connection between attributes and substances: "From this independent conceivability he infers that they can exist apart from one another, and hence, are really distinct. But this way of proceeding is only viable if Descartes can justify the pairing of thinking with non-extended and extended with non-thinking. Otherwise, he has no assurance that in conceiving of mind and body he is conceiving of diverse substances rather than one and the same substance conceived through diverse attributes." (Dutton 2003: 395) According to Dutton the attributes of thought and extension, as referred also to indivisibility and divisibility, are not enough to differentiate the substances of mind and body, jeopardizing the dualism. Nevertheless, Descartes defends his dualism on a strict differentiation mind and body as substances, and writes in Principle 60, 1: "Similarly, because each one of us understands that he thinks, and that in thinking he can shut off from himself every other substance, either thinking or extended, we may conclude that each of us, similarly regarded, is really distinct from every other thinking substance and from every corporeal substance." (Descartes 2000: 247). In other words, the separation of mind and body is for Descartes rooted in our power of thinking that cannot be alienated. The Cartesian dualism relies on the attributes rather than on the theory of substance but remains a substance dualism. C. Leibniz and the Cartesian dualism Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 17 According to Leibniz, the metaphysical weakness of the Cartesian mind/body union has its origin in the lack of acknowledgement by Descartes of the mutual dependence between substance and its attributes. In his Opuscules Philosophiques Choisis, Leibniz claims: "Also he falsely involved the bodily substance in extension, and misunderstood the union of soul and body, all because he misunderstood the nature of the substance in general." (Leibniz 1996: 80)1 Leibniz, in his comment of article 51, I, acknowledges that because substance and attributes need each other, it is necessary to draw a clearer distinction between substance and its attributes. He writes: "Since substance and accident require each other, it must be established other criteria in order to distinguish the substance of the accident." (Leibniz 1996: 32)2 Consequently, in his comment on article 52, I, Leibniz questions the choice of extension as main attribute of corporeal substance and writes: "It is however certain that neither movement nor action, nor resistance or passive force derive from extension." (Leibniz, 1996: 33)3 In writing so, Leibniz reproaches Descartes for his passive and weak metaphysical and epistemological conception of corporeal substance, and considers that the attribute extension cannot explain what occurs in bodies. For Leibniz, the Cartesian theory of the substances in relation to their attributes cannot explain the mind/body union. The passivity embedded in the notion of extension may explain difficulties encountered in the union between mind and body since we do not know where internal movement comes from. Leibniz does not think extension is a "primitive" notion because it does not express the action of extension of material substance. As in Descartes's philosophy, motion is not an attribute but a mode of matter, and could not be Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 18 interchangeable with substance while extension is. Regarding movement, Descartes writes to Mersenne on April 26, 1643: "Motion, and all other modifications of substance which are called qualities, have not greater reality, on my view, than is commonly attributed by philosophers to shape, which they call only a mode and not a real quality..." (Cottingham et al. 1991: 216) Leibniz, however, emphasizes that choosing motion or antitupia as the main attribute of the body is better than extension as a way of understanding the union between mind and bodies. In fact, motion would be a better attribute than extension to explain the internal movement and individuation of corporeal substances. Extension individualizes bodies by size, but does not account for form or internal movement. Because Leibniz does not rely on a dualism of substances but rather on a monist conception of substance, he needs to define more specifically and efficiently the attribute of the body. The Cartesian definition of mind and body is embedded in the spiritual and material substance and therefore underlines the separation between the science of the bodies and the metaphysics of substances. This separation takes place very early in the Cartesian system and claims to be based on clear and distinct foundations. Descartes's epistemology and metaphysics require that substances be known as spiritual and material, but the limits of perception preclude this ontological thesis. We will consider how and why this scission develops from very early on in the Cartesian system. Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 19 4. A NEW CONTEXT TO REFRAME CARTESIAN DUALISM Our previous analysis invites us to revisit the Cartesian dualism in the light of the role of the attributes in the substances, and the respective limits of science and metaphysics towards everyday experience. For instance, a different way to conceive dualism and the role of the senses in cognition appears in Descartes's early correspondence with Gassendi, and late correspondence with Princess Elisabeth, and Henry More. A. Common sense knowledge of mind and body When battling with his correspondents on the relationship between mind and body, Descartes was called to reflect on the foundation for his dualism of substances. Here we find a softened dualism as Descartes recognizes the conflation of attributes in his definition of substance. Two of his main correspondents, Gassendi and Henry More, debate him on this question; through close reading of Descartes's writings, we can detect whether a change occurred regarding the respective attributes of the two substances. In his work entitled The Metaphysical Meditations, Descartes sets out in Meditations II and VI the irreducible distinction between the two substances, the body whose nature is extension, and the mind whose nature is thought. Gassendi in his objections about Meditation II, disputes the Cartesian dualism between mind and body, quote: "You will have to prove that this solid body of yours contributes nothing whatever to your thought (for you have never been without it, and have so far never had any thoughts when separated from it). You will thus have to prove that you think independently of the body in such a way that you can never be hampered by it or disturbed by the foul and dense vapors or fumes which from time to time have such a bad effect on the brain." (Cottingham et al. 1984b: 183). Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 20 In this passage, Gassendi states that body should influence the mind, namely extension or mobility. In his answers to Gassendi's objections, Descartes refines his position and emphasizes that his knowledge of the mind and body is scientific, and not rooted in the everyday experience of the senses. Descartes defends his distinction of the nature of the mind and body in drawing a separation between knowledge for everyday life where senses are required to keep safe, and the search for truth that requires to be founded on certitude. He writes: "However we must note the distinction which I have insisted on in several passages, between the actions of life and the investigation of the truth...But when our inquiry concerns what can be known with complete certainty by the human intellect, it is quite unreasonable to refuse to reject these things in all seriousness as doubtful and even as false." (Cottingham et al. 1984a: 243). Here Descartes categorizes knowledge in an unusual way; the one that belongs to everyday life, and the one that belongs to philosophical and scientific knowledge. This new definition of knowledge is contrary to the Discourse on the Method where he had previously denied that common sense experience could be of any use in the attainment of knowledge. This shows that Descartes momentarily considered the separation of mind and body to be only valid within his theory of knowledge but not in reality. The two substances, identified as thinking mind and extended body, would then be a scientific and philosophical construction, but would not concern the realm of everyday life. In his correspondence with Gassendi, Descartes stresses that the relationship of soul and body may be an issue for some philosophers, but not for any person full of common sense. In fact, he reproaches Gassendi for being un-methodical, and for relying strictly upon everyday life experiences. Is he here simply recalling what he already developed at length in the Discourse and his Meditations, that is that everyday experience is useless in science, or is he setting limits to his own theory of knowledge? As a matter of fact, Descartes admits to Gassendi that there is knowledge acquired from everyday life, and Gassendi succeeds Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 21 in pushing him to define the limits of his own system. In distinguishing the two types of knowledge in this conversation, whether scientific or common, Descartes gives up his idea of a method to reach certain knowledge applicable to both his mechanistic science/philosophy and everyday life experience. Later, in his correspondence with Elisabeth, Descartes again adopts the same line of reasoning as with Gassendi, when he points out that our everyday life experience is appropriate for the understanding of the soul/body union. At the time of his debate with Gassendi, he had acknowledged that there is a kind of knowledge which comes from everyday experience but which is not philosophical or scientific knowledge. In his letter to Elisabeth of June 28th 1643, Descartes emphasizes that the understanding of this union between mind and body is rooted in the experience of everyday life: "...and finally what belongs to the union of the soul and the body is known only obscurely by the intellect alone or even by the intellect aided by the imagination, but it is known very clearly by the senses... . But it is the ordinary course of life and conversation, and abstention from meditation and from the study of the things which exercise the imagination, that teaches us how to conceive the union of the soul and the body." (Cottingham et al. 1991: 227) Descartes states clearly that knowledge of this union comes from the senses. To corroborate this analysis, there is a letter of Descartes to Chanut regarding the state of soul/body relation before birth. In a letter of February 1st 1647, Descartes seems to reveal the existence of an existential relationship between mind and body. He reflects on the origin of the soul/body union as follows: "But there is no doubt that the bodily conditions that were the first to accompany our thoughts when we came into the world must have become more closely Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 22 connected with them than those which accompany them later...I think that the soul's first passion was joy, because it is not credible that the soul was put into the body at a time when the body was not in a good condition.. The soul, uniting itself willingly to that new matter, felt love for it; and later, if the food happened to be lacking, it felt sadness." (Cottingham et al. 1991: 309) For Descartes, soul and body were united at the origin of life and the body was nourishing the soul. The independence of the soul begins when, after birth, we are able to abstract and the soul becomes mind. Originally soul and body are like one and the soul later on always remembers the first impressions coming from the body. The heterogeneity of mind and body developed all through the Cartesian corpus appears to be, in these letters, only a scientific explanation able to make clear their respective function. Descartes admits to Gassendi and Elisabeth that senses play a central role for the guidance of life in which philosophical considerations about mindbody dualism can be ignored. The structure of the Cartesian dualism plays solely a role to give a scientific and metaphysical explanation of the nature of mind and body. The dichotomy between the world of everyday life and the world of knowledge is acknowledged without denying the possibility to acquire metaphysical and scientific knowledge of mind and body. No epistemology is possible outside the framework of this dualism operating as a model for the scientist. B. Metaphysical approach of the extension of the spirits: debate with Henry More One of the main issues between Descartes and his friend the dualist Henry More is the concept of extension. According to Cartesian dualism, extension is solely applicable to bodies, has shape, un-penetrability, divisibility and measurability. More however conceives that God, angels, and the human mind also have extension, but that this extension is of another kind. In his letter of December 2nd, 1648, More embraces Cartesian dualism but nevertheless desires to amend it in order to give extension to spiritual substances: Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 23 "However, in order to conceal nothing, Sir, though I am madly in love with your system, and the whole body of your philosophy, I confess there is something you missed in the second part of your principles ... But these difficulties do not wear blow to the core of your philosophy ...." (Monnoyeur 2004). In his letter of February 5th 1649, Descartes explains his view at length on the nature of extension, and refuses to follow More, who attributes extension to any substance. In his reply to Descartes of March 5th 1649, Henry More insists that spiritual extension is fundamental to material extension. Geneviève Rodis-Lewis (1984) labeled this debate on extension "a dialogue between deaf people" in order to underline the absence of understanding between the two dualists. This opinion can perhaps be challenged by the fact that More praised Descartes for his dualism, and convinced him that they were arguing merely about words. The following passage proves that Descartes is receptive to More's argument. In his answer to Morus of April 15th, 1649 Descartes quotes Henry More about the existence of spiritual extension: "I say that there is another, equally genuine, extension" and brings the following comments: "At last we are in substantial agreement; there only remains a question of terms, whether this second sort of extension is to be called equally genuine. For my part, in God and angels and in our mind I understand there to be no extension of substance, but only extension of power...But to attribute to a substance an extension which is only an extension of power is an effect of the preconceived opinion which regards every substance, including God himself, as imaginable." (Cottingham et al. 1991: 372). Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 24 Descartes concludes the debate by naming this spiritual extension: extension of power. Here we have a concession on the attribute of extension that had been so essential for the clarity of understanding bodily substance. Descartes explains a few lines later that this spiritual extension represents the power of spiritual substance to act upon material substance and vice versa. Descartes adds: "In fact, if there was no corporeal extension, I could not conceive any space to which an angel or God would be coextensive." (Cottingham et al. 1991: 372). We can therefore conclude that Descartes acknowledges a power of extension to immaterial beings, and proper to spiritual substances. In writing so, it seems that Descartes tries to make sense of the attribute extension not only for the spiritual substances but also for his whole system. But this kind of defense against More's objections seems to betray the earlier conception of spiritual substance. Extension had been the unique property of bodily substance and is now applicable to spiritual substances. However, this contradiction does not mean that Descartes became a monism and went further than Henry More who was a dualist. This certain kind of extension attributed now to spiritual substances emphasizes the important role of attributes in the Cartesian conception of substance. Our analysis of the correspondence with Gassendi and More has shown how complex and rich the Cartesian dualism is. We have seen how, in his correspondences, Descartes is seriously considering the objections to his system, accepting what he earlier refused; that is to say, the existence of knowledge based on everyday life and the need for an extension of power for spiritual substances. He seems then to have departed from a theory of knowledge based on a strict thought/extension dualism. Henry More developed a new type of dualism in his Enchiridum Metaphysicum. Extension is a common attribute of mind and body but with specific characteristics in each of Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 25 the substance (Monnoyeur 2004). In spirits, extension is penetrable but impenetrable in bodies. We can envision how Henry More in his correspondence could have convinced Descartes to embrace a form of dualism closer to his dualism. It seems to me that Descartes did not change his mind about the nature of his system, but is occasionally ready to challenge his thought/extension dualism. Machamer and McGuire may have convinced themselves that Descartes abandoned his dualism and adopted a new epistemology because of lack of confidence in human mind capacity to reach the nature of substances. In fact, Descartes just drew a line between knowledge of everyday life and metaphysical knowledge. There is useful knowledge for life coming from experience but not included in scientific and metaphysical knowledge. Also, the same mitigating concessions about the extension of spiritual substances can be found in earlier works and obviously did not cause him not to develop his dualism in the first place. Descartes's so called dualism is challenged by his theories of substances and attributes, and the way they interact among themselves. 5. CONCLUSIONS Peter Machamer and J.E. McGuire made the point that according to Descartes our mind is too limited to reach absolute knowledge. We have denied that this was Descartes's intention and shown that in his view both metaphysics of substance and everyday experience inform us about the way to understand the world, in particular the mind/body union. This type of knowledge depends upon the senses and the mind rather than the mind alone. For instance our acknowledgment of the union between soul and body stems from sensitive knowledge. The authors consider that Descartes 'loses philosophical ground' when it comes to discover the essence of substances and re-orients his theory of knowledge towards a more pragmatic Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 26 purpose. In my view, Descartes does not modify his system of knowledge or belief according to which he can reach truth in sciences and build his metaphysics; rather he admits early to Gassendi that common knowledge concurs with rational knowledge in everyday life. He later accepts in his correspondence with Henry More that spirits have something to do with the extension of bodies. But these two points do not contradict his dualism based on the separation of the substances mind and body, and underline the role of the main attributes in his substance dualism. At no time, Descartes re-evaluates the validity of his dualism and his theory of substance that is the bedrock of his philosophy; he merely concedes to his objectors, Gassendi and Henry More. He does not take these concessions as serious threats to his conception of substance and dualism. It is nevertheless a fact that Cartesian dualism is based on a shared role of substance with its attributes, and neglects, as Leibniz underlines, the role of substances as individual subjects. As mind and body do not identify totally with their attributes thought and extension, these attributes bear the burden of his dualism. Descartes's theory of the substances and their union emphasizes the role of attributes in his dualism, and appreciation of this role puts in proper perspective his epistemic shift4. NOTES 1 Translated from French by the Author. The original text is: "Aussi a-t-il fait faussement consister la substance corporelle dans l'étendue, et il a mal compris l'union de l'âme et du corps, tout cela faute d'avoir compris la nature de la substance en général." (Leibniz 1996 : 80) 2 Translated from French by the Author. The original text is: "Puisque la substance et l'accident s'exigent mutuellement, il faut établir d'autres critères, afin de pouvoir distinguer la substance de l'accident;" (Leibniz 1996: 32) 3 Translated from French by the Author. The original text is: "Il est cependant certain que ni le mouvement ou l'action, ni la résistance ou la force passive ne dérivent de l'étendue, comme je Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 27 l'ai montré ailleurs. En effet, la notion d'étendue n'est pas primitive, mais peut être décomposée." (Leibniz, 1996: 33) 4 I am grateful to Dante Diotallevi (Queen's University, Canada) for his critical reading and suggestions, to Thomas Steinbuch (Hangzhou University, China) for his comments, and I would also like to acknowledge the two anonymous reviewers for their precious help. REFERENCES Descartes, René. 2000. Philosophical Essays and Correspondences. Translated and edited by Roger Ariew. Cambridge: Hackett Publishing Company, Inc. Cottingham, John, Robert Stoothof, Dugald Murdoch, and Anthony Kenny, trans. and eds. 1984a. The Philosophical Writings of Descartes: Vol 1. Cambridge: Cambridge University Press. __________. 1984b. The Philosophical Writings of Descartes: Vol 2. Cambridge: Cambridge University Press. __________. 1991. The Philosophical Writings of Descartes: Vol 3. Cambridge: Cambridge University Press. Dutton, Blake. 2003. "Descartes's Dualism and the One Principal Attribute Rule." British Journal for the History of Philosophy 11(3): 395–415. Gaukroger, Stephen. 2002. Descartes' System of Natural Philosophy. Cambridge: Cambridge University Press. Kaufman, Dan. 2008. "Descartes on Composites, Incomplete Substances, and Kinds of Unity". Archiv für Geschichte der Philosophie 90: 39–73. Final Version accepted to be published in Journal of Philosophical Research Vol 41 * January 2017 28 Leibniz, Gottfried Wilhelm. 1966. Opuscules philosophiques choisis. Translated and edited by Paul Schrecker. Paris: Vrin. Machamer, Peter and J. E. McGuire. 2009. Descartes's Changing Mind. Princeton: Princeton University Press. Moonoyeur, Françoise. 1992. La matière et l'espace dans la philosophie première de Descartes. Poitiers: Bibliothèque Universitaire de l'Université de Poitiers. __________________ 2004. "Henry More: plaidoyer pour un espace infini." In Infini des philosophes, infini des astronomes, ed. Françoise Monnoyeur. Paris: Editions Belin, 77-92. Rodis-Lewis, Geneviève. 1984. Descartes, textes et débats. Paris: Livre de Poche. 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