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A work in Process by, Brennen "china" Ryan
From Descartes's day to the present, the criticism has been made against Descartes that his dualism does not allow the interaction between substances: If mind and body are distinct, then their interaction is impossible. Starting from at least the end of The Meditations to his later works, his letters to Princess Elizabeth and The Passions of the Soul, Descartes developed a picture of mind and body union as a functional composite. In his later work, Descartes saw the problem of substance interaction as connected with the problem of mind and body union. I would like to see how his portrayal of mind and body union as a functional composite might throw light on, and weaken, the criticism about the impossibility of substance interaction.
To understand the criticism, it is necessary to review the distinction between the substances and why they are distinct. Descartes claim is not just an epistemological claim that for all we know the world is composed of two distinct substances, rather it is the stronger claim that the world is composed of two distinct substances. In The Principles Descartes states a reason for claiming that there are two distinct substances. He links the claim that they are distinct to the claim that we can understand mind and body apart from each other, "a real distinction exists only between two or more substances; and we can perceive that two substances are really distinct simply from the fact that we can understand one apart from another (AT vol. I 28, CSM vol. I 213). This claim alone is not strong enough to get Descartes to the real distinctness that his metaphysics requires. The Sixth Meditation is where we can find a more complete argument for the real metaphysical distinction between mind and body.
Descartes begins with the conceivability-possibility principle. This principle states that whatever can be conceived clearly and distinctly is possible and what is possible can be clearly and distinctly perceived. "I know that everything which I clearly and distinctly understand is capable of being created by God so as to correspond exactly with my understanding of it" (AT vol. II 78, CSM II 54). If I conceive clearly and distinctly an object as such and such, then I am able to infer the possibility of the object existing as such and such. For example, from the clear and distinct conception of the mind existing apart from the body, Descartes infers the possibility of the mind existing apart from the body (Rorty 79). A clear and distinct conception allows us to infer the possibility of what is conceived.
The epistemic argument of the Second Meditation that my nature as far as I know is a thinking thing is strengthened in the Sixth. In the Sixth, Descartes argues that my nature as such is a thinking thing (AT vol. II 78, CSM vol. II 54). From, "I know I exist and am a thinking thing", Descartes does not just infer that "it is possible that I am a thinking thing", rather, he infers, "my essence is solely that I am a thinking thing" (AT vol. II 78, CSM vol. II 54). What allows him to make this stronger claim is the fact that he has no other clear and distinct conceptions about his nature. There are no other candidates for what his nature is except that he is a thinking thing. "Thus simply knowing that I exist and seeing at the same time absolutely nothing else belongs to my nature or essence except that I am a thinking thing" (AT vol. II 78, CSM vol. II 54).
To make the assertions about his actual nature requires the conceivability-possibility principle and three premises: 1. I exist. 2. I have a clear and distinct conception that I am a thinking thing. 3.There are no other clear and distinct ideas about my nature. Descartes moves from the conceivability-possibility principle to the positive conclusion that the mind's nature is a thinking thing goes something like this: Descartes has a clear and distinct idea that his nature is thinking. Since this is a clear and distinct idea, it is possible. Since there are no other clear and distinct ideas about the mind's nature, the sole clear and distinct idea must not just be possible, but actual. Therefore, "on the one hand... I am simply a thinking, non- extended thing" (AT vol. II 78, CSM vol. II 54), he adds, "...on the other hand I have a distinct idea of body, insofar as it is an extended, non-thinking thing" (AT vol. II 78, CSM col. II 54).
At the very least, this distinction suggests that the essence of thinking in no way involves the essence of extension. "[I]t is certain that I am really distinct from my body, and can exist without it" (AT vol. II 78, CSM vol. II 54). What is important here is that the real distinction argument is an argument for the separability of mind and body, not separation. Because I can clearly and distinctly understand mind apart from body, I can understand them as capable of being separated, and as two separate substances. "The fact that I can clearly and distinctly understand one thing apart from another is enough to make me certain that the two things are distinct, since they are capable of being separated, at least by God" (AT vol. II 78, CSM vol. II 54). The claim that the mind and body are separable, and not necessarily separated, opens the possibility that they are continently joined in some way. Descartes writes to Huygens, 31 January 1642, "[W]e meant this only in relation to its parts, the soul and the body; we meant that for each of these parts it is in a manner accidental for it to be joined to the other, because each can subsist apart..." (AT vol. III 508, CSM vol. III 209).
II. The Problem of Substance Interaction
There are different versions of the objection that the mind and the body cannot possibly interact. This is the origin of the claim that Today Cartesian dualism lacks scientific credentials, or worse, is in conflict with a modern scientific outlook. After all, if Descartes's dualism is right, so the critics argue, then there is a substance that has a causal impact on the world, yet is in no way explicable in terms of physics, thus the physical world is not a closed system. In Descartes's terms, mind-body interaction requires that new motions are introduced into the world, and that violates Descartes's conservation of motion principle. The physical world is the mathematical world as realized by God who sets in motion and preserves the same quantity of motion in matter. Concerning the amount of motion, the physical world is a closed system. Introducing motions from outside the physical world is inconsistent with the principle that the same amount of motion is always preserved. Here Descartes' metaphysics is inconsistent with his physics.
A related objection made in a different way by critics such as the materialist Pierre Gassendi and Princess Elizabeth of Bohemia. Gassendi raises the objection to Descartes's Meditations:
You must explain to us how this 'directing' of movement can occur without some effort - and therefore motion – on your part. How can there be some effort directed against anything, or motion set up in it, unless there is mutual contact between what moves and what is moved? And how can there be contact without a body when, as is transparently clear by the natural light, 'naught apart from the body, can touch or yet be touched' (AT vol. II 341, CSM vol. II 237).
Later, in a letter to Rene Descartes, dated 16 May 1643, Princess Elizabeth of Bohemia raises a number of questions about the relation of the mind to the body. Her objections are similar to Gassendi's. She asks, if the laws of motion require physical contact between extended bodies for a transfer of motion to take place, then how can something that is immaterial and non-extended move something extended, namely, the pineal gland. Descartes phrases the objection in the Appendix to the Fifth Set of Replies and Objections as, "how can the soul move the body if it is in no way material[?]" (AT vol. II 213, CSM vol. II 275). I'll dub this second problem the problem of difference, because critics who raise this objection think there is a problem in the mere fact that substances so different as mind and body can interact with one another. ***We will later see how Descartes's theory of causality and his theory of mind and body union as a functional composite weaken these two related objections. ***
In both the Appendix to the Fifth Set of Replies and Objections and his letters to Elizabeth, Descartes responds in a similar way. Two things are important to notice about his responses. First, Descartes claims that the objection raised against mind-body interaction is based on a false or confused notion of causation among his critics. In physics, Descartes tried to remove from his physics the occult properties of causation and relations found in the scholastic and magical traditions. These traditions inherited a model of explanation from Aristotle that appealed to teleological causation, formal causation, material causation, and efficient causation. Within his physics, Descartes narrowed his notion of causality to only that kind of causality found between two objects in the physical world. His physics restricted causality to efficient, mechanistic, causality. However, when considering mind body causation, Descartes adopted a wider version of causality than that of his physics. The causation between mind and body is different than the causation between bodies. Descartes think that failure to notice this difference is the source of confusions on the part of his critics. To Elizabeth, he writes, "[s]o I think we have confused the soul's power to act on another body with the power one body has to act on another" (AT vol. III 667, CSM vol. III 219). To Huygens, 31 January 1642, Descartes makes explicit the false assumption underlying the objections of his critics, "But I will say... that the whole problem contained in such questions arises simply from the supposition that is false and cannot in any way be proved, namely that, if the soul and the body are two substances whose nature is different, this prevents them from being able to act on each other" (AT vol. II 213, CSM vol. II 275).
The second important fact about his replies is that he insists that the problem of substance interaction should be embedded in the problem of mind-body union. To Huygens, 31 January 1642, he writes, "These questions presuppose among other things an explanation of the union between the soul and the body..." (AT vol. II 231, CSM vol. II 275). With an expanded notion of causality and a picture of mind-body union as a functional composite, we can begin to make Descartes's portrayal of substance interaction more plausible than is sometimes portrayed.
Wider Notion of Causality
What is Descartes wider notion of causality?
In his first attempt to convince Elizabeth, Descartes uses am analogy of how the weight of an object causes it to fall, "For instance, when we suppose that heaviness is a real quality, of which all we know is that it has the power to move the body that possesses it toward the center of the Earth, we have no difficulty in conceiving how it moves this body or how it is joined to it" (AT vol. III 667, CSM vol. III 219). He suggests that this kind of paradigmatic case of causal interaction is how we come to understand other cases of interaction. "For I believe that it [the notion of heaviness] was given to us for the purpose of conceiving the manner in which the soul moves the body" (AT vol. III 668, CSM vol. III 219).
Mind as triggering cause in this case
Picture of Mind-Body Union as a Functional Composite
Undermining the Critics
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