The problem of mental causation is a central problem in the metaphysics of mind, but hylomorphism implies an elegant solution to it.
Here’s a version of the problem I discuss in Structure and the Metaphysics of Mind:
- Actions have mental causes.
- Actions have physical causes.
- The mental causes and the physical causes of actions are distinct.
- If actions have multiple causes, then they are overdetermined.
- Actions are not overdetermined.
Claims (1) – (3) imply that actions have multiple causes, and claims (4) – (5) imply that they do not. The five claims are thus jointly inconsistent: they cannot all be true, and yet there are well rehearsed reasons to accept each.
Because hylomorphists endorse the existence of emergent properties with the characteristics described in my earlier post, they cannot reject claims (1) or (3), nor can they reject claim (2) because they also claim that higher-level behavior never violates lower-level physical laws. If the lower-level constituents of a structured whole were to lose their powers, they would become incapable of composing the activities of the whole. Those activities depend on lower-level items retaining and manifesting the powers they have.
By analogy, it is only because bricks and timbers retain their shapes under compression that they can be recruited as components of buildings. Similarly, it is only because lower-level materials retain their distinctive powers that structured individuals can recruit them as components for their own activities. This is one thing that sets the hylomorphic view apart from those classic emergentist theories such as Roger Sperry’s which claim that higher-level powers trump or nullify the powers of lower-level things.
That leaves claims (4) and (5). Between them, hylomorphists target (4). Claim (4) is true, say hylomorphists, only on the assumption that the mental causes and physical causes are causes of the same type. But hylomorphists reject the assumption that there is only one kind of causal relation, and they take explanations of human behavior that appeal to thoughts, feelings, and perceptions, on the one hand, and explanations of human behavior that appeal to physiological mechanisms, on the other, to correspond to different kinds of causes.
Thoughts, feelings, and perceptions contribute to actions in one kind of way, physiological mechanisms in another. The former contribute insofar as they are ways in which human behavior is structured; the latter contribute insofar as they are things whose activities get structured. Structure in general is different from materials or events that get structured—that’s what it means to say that structure is a basic ontological and explanatory principle.
Accordingly, reason-based explanations of human behavior and mechanistic explanations of human behavior pick out different kinds of causal relations on the hylomorphic view. As a result, they cannot overdetermine actions. Overdetermination in the relevant sense implies that the overdetermining causes contribute to their effects in the same way—paradigmatically each is by itself a sufficient cause. But that is not the case here. By analogy, high blood-alcohol levels and faulty brakes both contribute to car crashes, but they are not overdetermining causes of crashes; the reason is that they contribute to crashes in different ways. There is thus no threat of actions being overdetermined by thoughts, feelings, and perceptions, on the one hand, and by physiological mechanisms, on the other. Claim (4) is thus false on the hylomorphic view.
This distinction among kinds of causal relations enables hylomorphists to rewrite claims (1) – (5). To appreciate how, it will be helpful to coin some terms to express the different ways in which mental causes and physiological causes contribute to behavior. Let us say that thoughts, feelings, and perceptions rationalize actions, and that neural events trigger the muscular subsystems involved in actions. Claims (1), (2), and (3) can then be rewritten as follows:
(1′) Actions are rationalized by thoughts, feelings, and/or perceptions.
(2′) Muscular contractions are triggered by events in the nervous system.
(3′) Rationalizing causes and physiological triggers are distinct.
These claims are jointly consistent, and hylomorphists can endorse all three. Claim (5) can be rewritten in a variety of ways. Here are two possible formulations:
(5′) An action does not have more than one rationalizing cause.
(5′′) An action does not have more than one physiological trigger.
Both of these claims as well as their denials are consistent with (1′)–(3′). Consequently, whether hylomorphists endorse (5′) and (5′′) or deny either, they end up solving the problem.
One thing to note about the hylomorphic solution: it implies that the arrow diagrams made popular by Jaegwon Kim for discussing the problem of mental causation are misleading (Figure 1).
Kim’s diagrams have been enormously influential, but according to hylomorphists, they misrepresent human action in at least two ways. First, they suggest that there is only one kind of causal relation which is represented by the arrows. Second, the arrows suggest that the kind of causal relation involved is a triggering relation; they do not capture the distinctive character of rationalizations. A better representation of actions depicts physiological conditions, along with social, psychological, and environmental ones, as necessary factors that contribute to the occurrence of an action in different ways (Figure 2).
On the hylomorphic view actions are complex structured phenomena which comprise many different causal factors that contribute to their effects in many different kinds of ways. No one of these factors can qualify as the exclusive cause of the action. Consequently, thoughts, feelings, and perceptions, on the one hand, and physiological mechanisms, on the other, do not compete to occupy a single causal role: the role of being the one and only cause of an action. As a result, there can be no real worry about overdetermination even though the view comprises many causal factors.
In the next post I consider one of the most commonly heard objections to the hylomorphic view.