This post continues my critique of hylomorphic dualism in the philosophy of mind. (See Hylomorphism category.) I will argue that hylomorphic dualism inherits one of the difficulties of compound substance dualism. But to understand the latter, we need to contrast it with simple or pure substance dualism. By 'substance' I mean primary substance, prote ousia in roughly Aristotle's sense. (But I hope to avoid exegetical bickering.) S is a primary substance if and only if S is broadly logically capable of independent existence.
A. Simple or Pure Substance Dualism. This is the view that I am identical to my soul or mind. (And the same goes for you.) In Cartesian terms, I am identical to a res cogitans, a thinking thing or thinking substance. If so, my body is not a part of me. I am not a compound of soul and body; I am a simple substance.
B. Compound Substance Dualism. This is the view that I am a composite of soul and body, which implies that my body is a proper part of me. Thus I have two proper parts, soul and body, the first essential to me, the second accidental. I cannot exist without my soul, but I can exist without my body, where 'can' expresses broadly logical possibility.
(A) and (B) are mutually exclusive. Assuming the truth of Cartesian dualism, they are also jointly exhaustive. So if you are a Cartesian dualist, you must choose between saying that you are your soul (mind) or that you are not your soul but a composite of soul and body.
C. Hylomorphic Dualism. This is the view that I am a compound of soul and body, but with the difference that the soul is the form of the body. Anima forma corporis. The idea is not that the soul is like a form or analogous to a form, but that the soul is a form. Hylomorphic dualism is not a species of Compound Substance Dualism for the simple reason that form and matter are 'principles' invoked in the analysis of primary substances but not primary substances themselves. But it is dualistic in that mind and body are mutually irreducible. A form is not a primary substance because it is not broadly logically capable of independent existence.
A Problem with Compound Substance Dualism
Suppose we ask a simple question. Using 'think' in the broad Cartesian way, to cover all manner of intentional states including perceiving, imagining, remembering, etc., who or what is it that thinks when I think? Who or what is the subject of thinking? There are only two possibilities given the above. Either a soul thinks when I think, or a soul-body composite thinks when I think. (The brain no more thinks than my eyeglasses see.)
The Compound Substance Dualist must say that a soul-body composite thinks when I think. Now soul = mind = thinking substance (res cogitans). So CSD implies that when BV thinks there are really two thinkers, the thinking substance which is a proper part of BV, and the whole BV as soul-body composite. (The point is made in a different way by Eric T. Olson in "A Compound of Two Substances" in Soul, Body, and Survival, Corcoran ed., Cornell UP 2001, p. 75.) Here is the way Olson puts it:
. . . compound dualism entails that there are at least twice as many thinking things as we thought there were. You are a compound of a body and a soul. But that soul is itself rational and conscious. So there are two thinking things sitting in your chair, a soul and a compound, reading an essay that was co-written by simple and a compound philosopher.
Obviously, this won't do. Well, why not just say that the soul does not think, that only the compound thinks? One might say that soul and body are each sub-psychological, and that to have a psyche and psychic activity (thinking), soul and body must work together. Soul and body in synergy give rise to thinking which qualifies the whole man. But this makes hash of substance dualism. For one of the reasons for being a substance dualist in the first place is the conceivability of disembodied thinking. (We'll have to look at Kripke's argument one of these days.) Disembodied thinking is obviously inconceivable if it is a soul-body composite that thinks. Second, if it takes a soul and a body working together to produce thinking, then the soul is not a mind or thinking substance — which again makes hash of substance dualism.
For these and other reasons, CSD is to be rejected, and simple or pure dualism is to be preferred if one is to be a substance dualist.
Hylomorphic Dualism Faces a Similar Problem
Now let's confront the hylomorphist dualist with the question about the subject of thinking. Who or what thinks when thinking occurs in BV? For the HD-ist it is the composite of soul and body, form and matter. Thus the soul by itself is subpsychological and so does not think: the subject of thinking, that which thinks, is the soul-body composite. But when we turn to the 'king' of the hylomorphic dualists, Thomas Aquinas, we find him saying things about the intellect that run directly counter to this.
In the Summa Contra Gentiles, Book II, chapters 49-51, we find a variety of arguments to the conclusion that the intellect is a subsistent form and so not dependent for its existence on matter. This is not the place to examine these arguments, some of which are defensible. Now since the intellect is that in us which thinks, the same ambiguity we found in Cartesian dualism, as between pure dualism and compound dualism, is to be found in Aquinas. Is it the composite that thinks, or a part of the composite? The answer must be that it is a part of the composite that thinks, the res cogitans on the Cartesian view, the intellectus on the Thomist view. And note that both must be viewed as substances, as capable of independent existence. Aquinas expresses this by referring to the soul as a subsistent form.
But 'subsistent form' smacks of contradiction. How can a form be subsistent? To say that a form is subsistent is to say that is is a primary substance, that is is broadly logically capable of independent existence. But a form is precisely not a primary substance but a 'principle' invoked in the analysis of primary substances. Aquinas cannot do justice to his own insight into the independence of the intellect from matter from within the hylomorphic scheme of ontological analysis he inherits from Aristotle. This bolded (and bold) thesis is central to my critique of hylomorphic dualism. His metaphysica generalis is at war with his special-metaphysical insight into the independence of intellect from matter.
Let me spell this out just a bit. Aquinas' method of ontological analysis is hylomorphic, in terms of matter (hyle, materia) and form (morphe, forma). He applies this type of ontological analysis across the board. Of course, the world is not form and matter 'all the way down': this style of analysis reaches a limit with materia prima, prime matter. Nor is the world form and matter 'all the way up': this style of analysis reaches a limit with God who is pure form, the "form of all forms" (forma formarum). These limits, however, remain within the ambit of hylomorphic analysis and do not show that the analysis does not hold across the board. So, naturally, Aquinas applies this style of analysis to minds.
So I cannot see that hylomorphic dualism is any improvement over pure substance dualism. It is rather a step backward. And as I tried to show here the notion that HD can solve the interaction problem — assuming as I do not that it is a genuine problem — is chimerical.