Determinables, Determinates, and Causal Relevance

Determinables, Determinates, and Causal Relevance

Mental causation, our mind's ability to causally affect the course of the world, is part and parcel of our 'manifest image' of the world. That there is mental causation is denied by virtually no one. How there can be such a thing as mental causation, however, is far from obvious. In recent years, discussions about the problem of mental causation have focused on Jaegwon Kim's so-called Causal Exclusion Argument, according to which mental events are 'screened off' or 'preempted' by physical events unless mental causation is a genuine case of overdetermination or mental properties are straightforwardly reducible to physical properties. In response to this line of reasoning, Stephen Yablo pointed out that any alleged exclusion of mental properties by physical properties can be avoided if we treat the former as determinables of which the latter are determinates (see Yablo, 1992, 1997, 2000, 2001; see also MacDonald & MacDonald, 1986). Yablo's idea that we may think of the mental/physical distinction as an instance of the determinable/determinate distinction is an interesting and original suggestion which so far has received little attention in the debate about the problem of mental causation. In this paper, I examine Yablo's position, arguing that in the end the determinable/determinate distinction is unlikely to yield a satisfying (dis)solution of Kim's Causal Exclusion Argument. Taken literally, the claim that mental properties are related to physical properties as determinables are related to determinates is false; understood more liberally, although true, it cannot deprive the Causal Exclusion Argument of its force.

I Causal Exclusion and the Determinable Hypothesis

In what follows, I will talk about the causal relevance of (mental) properties, as opposed to the causal efficacy of (mental) events. What does that mean? I take events to be Davidsonian datable, non-repeatable, object-like particulars (and not, like Kim, exemplifications of properties by objects at times). Events are causes, and an event which is a cause is (thereby) causally efficacious. Moreover, events cause what they cause because of how they are, i.e. in virtue of some of their properties and not in virtue of others. The properties in virtue of which a cause causes an effect are causally relevant (for the particular causal transaction in question, not necessarily per se). To take a famous example, the soprano's singing (event c) causes the window's shattering (event e), but c's being the singing of a word with a certain meaning is causally irrelevant for its causing e, whereas its being the singing of a high C is causally relevant (see Dretske, 1989).²

Given this terminology, the question raised by Kim's Causal Exclusion Argument is whether mental properties are causally relevant: do mental events cause what they cause in virtue of their physical properties, in virtue of their mental properties, or perhaps both?

According to the Causal Exclusion Argument,³ irreducible mental properties are inevitably preempted by physical properties, so that, barring overdetermination, non-reductive physicalism is committed to property epiphenomenalism, i.e. to the claim that events can be causes in virtue of physical properties, but not in virtue of mental properties (see McLaughlin, 1989). Roughly, Kim's argument goes as follows. Suppose c's having a mental property M is causally relevant for e's having a mental property M*. Assuming that M* supervenes upon a physical property P* of e — a minimal commitment of any physicalist theory (see Kim, 1998, 15) — e's having P* is non-causally sufficient for e's having M*. This creates a tension between M and P*: Does e have M* because c has M or because e has P*? Resolving this tension, Kim submits, requires assuming that c's having M is causally relevant for e's having M* in virtue of being causally relevant for e's having P*. In Kim's terminology: 'M caused M* by...