Jaegwon Kim’s discussions of the problem of mental causation have been enormously influential, so it should come as no surprise that some critics have tried to apply his reasoning to the hylomorphic solution discussed in Part 1.
Kim argued that nonreductive physicalism evacuates psychological discourse of any real explanatory content. Critics make an analogous charge against hylomorphism:
- If hylomorphism is true, then all of an individual’s intentional actions are necessitated by lower-level physical conditions.
- If all of an individual’s intentional actions are necessitated by lower-level physical conditions, then what explain those actions are the lower-level physical conditions that necessitate them.
- If what explain an individual’s actions are the lower-level physical conditions that necessitate them, then an individual’s thoughts, feelings, and perceptions do not explain that individual’s actions.
Therefore, if hylomorphism is true, an individual’s thoughts, feelings, and perceptions do not explain that individual’s actions.
Hylomorphists respond that there is an ambiguity in the notion of explanation that the argument appeals to. When explanation is understood one way, premises (2) and (3) are both false; when understood another way, they are both true but the conclusion does not follow. Either way, the argument fails, and hylomorphists argue that the conclusion is false as well.
The reasoning behind premise (1) appeals to the embodiment thesis that hylomorphists endorse. The kind of hylomorphism I’ve described is committed to the essential embodiment of all our capacities. Given reasonable assumptions this embodiment thesis implies robust supervenience and necessitation theses which imply that physical twins must be structural twins: things that are exactly the same physically must be exactly the same structurally. There can be no structure inverts or structure zombies: things that are physically exactly the same that yet differ from each other structurally. You and a physical replica of you would both be structured humanwise, and if you were in the same kinds of environments, you would both embody the same kinds of capacities, and would both engage in the same kinds of activities.
The prima facie case for premise (2) trades on a common misunderstanding of supervenience and necessitation relations. That misunderstanding takes necessitation (and/or supervenience) to imply some type of explanatory condition: it assumes, in other words, that if X necessitates Y, then X somehow explains Y. But the falsity of this claim was established by Jaegwon Kim (1984, 1990), Thomas Grimes (1988), and others in the late 1980s. It is among the best established results in all philosophy of mind.
To say that A-properties are necessitated by (or strongly supervene upon) B-properties is to say the following:
Necessarily, for any x, if x has an A-property, F, then there is a B-property, G, such that x has G, and necessarily, for any z, if z has G, then z has F.
What necessitation does not say is that things are explained by what necessitates them. The definition of necessitation includes no clause to the effect that that z’s having G explains its having F, or that x has F because it has G.
On its face, then, the claim that necessitation implies an explanatory condition is simply inaccurate; it freights in something that simply isn’t there. This is especially clear when we see the wide variety of metaphysical frameworks that are compatible with psychophysical necessitation: the psychophysical identity theory, eliminative physicalism, psychophysical parallelism committed to pre-established harmony, and emergentist or epiphenomenalist theories committed to brute laws of emergence. All of these views imply a commitment to psychophysical necessitation, and yet what explains the necessitation in each case is different.
Contrast especially a strong form of eliminativism and parallelism. According to strong eliminativism there can be no mental properties. Psychophysical necessitation thus follows trivially. What explains why an individual has mental properties on this view? Since nothing has mental properties nothing explains it. By contrast, suppose God ordains that in every possible world mental properties covary with physical properties in the way necessitation states. What explains why an individual has mental properties on this view? God’s ordination does. Necessitation by itself implies no explanatory condition.
Premise (2) of the objection is therefore false: necessitation does not imply explanation, at least not explanation in the sense critics intend—a sense according to which mental and physical causes compete to occupy a single causal role: the role of being the one and only cause of an action. We’ve seen that according to hylomorphists there is no such role.
The physical conditions that necessitate actions do explain them in some sense; namely, they answer how-questions of mechanism by describing the subsystems whose activities are able to be structured action-wise. But these explanations are different from reason-based explanations, which explain why an individual imposed this or that action-wise structure on the activities of his or her parts on a particular occasion.
That is why premise (3) is false as well. Simply because an individual’s actions are explained by the lower-level physical conditions that necessitate them in some sense (the how-mechanical sense), it does not follow that an individual’s thoughts, feelings, and perceptions do not explain actions in some other sense, such as the rationalizing, why-structural sense.
Hylomorphists can offer to rewrite claims (2) and (3) to make them true:
(2*) If all of an individual’s intentional actions are necessitated by lower-level physical occurrences, then those occurrences explain how (mechanistically) an individual’s actions are able to occur (that is, the explanations citing those occurrences describe subsystems whose activities are able to be structured action-wise).
(3*) If lower-level physical occurrences explain how (mechanistically) an individual’s actions are able to occur, then an individual’s thoughts, feelings, and perceptions do not explain how (mechanistically) an individual’s actions are able to occur (that is, rationalizing explanations do not describe subsystems whose activities are able to be structured action-wise).
Both of these claims are true according to hylomorphists, but from these claims the objection’s conclusion does not follow. It does not follow that an individual’s thoughts, feelings, and perceptions do not explain that individual’s actions on the hylomorphic view. Rather, we’ve seen that according to hylomorphists, thoughts, feelings, and perceptions do explain an individual’s actions; they rationalize those actions. The objection’s conclusion is thus false. Given hylomorphists’ commitment to causal pluralism—a causal pluralism grounded in a metaphysics of structure—there is no way of constructing an analogue of Kim’s criticism of nonreductive physicalism.
I consider a variety of other objections to the hylomorphic view as well as a variety of hylomorphic responses in Structure and the Metaphysics of Mind: How Hylomorphism Solves the Mind-Body Problem.
Grimes, Thomas R. 1988. The Myth of Supervenience. Pacific Philosophical Quarterly 69: 152–160.
Kim, Jaegwon. 1984. Concepts of Supervenience. Philosophy and Phenomenological Research 45: 153–176.
Kim, Jaegwon. 1990. Supervenience as a Philosophical Concept. Metaphilosophy 21: 1–27.