Functionalism, Mental Causation, and the Problem of Metaphysically Necessary Effects 1

The recent literature on mental causation has not been kind to nonreductive, materialist functionalism ('functionalism', hereafter, except where that term is otherwise qualified). The exclusion problem 2 has done much of the damage, but the epiphenomenalist threat has taken other forms. Functionalism also faces what I will call the 'problem of metaphysically necessary Functionalist mental properties are individuated partly by their relation to the very effects those properties' instantiations are thought to cause. Consequently, functionalist causal generalizations would seem to have the following problematical structure: The state of being, among other things, a cause of e (under such-and-such conditions) causes e (under those conditions). 3 The connection asserted lacks the contingency one would expect of a causal generalization. Mental states of the kind in question are, by metaphysical necessity, causes of e; any state that does not cause e is thereby a different kind of state. Yet, a mental state's being the sort of state it is must play some causal role if functionalism is to account for mental causation. 4 In what follows, I first articulate more fully the problem of metaphysically necessary effects. I then criticize three functionalist attempts to solve the problem directly. Given the failure of functionalist efforts to meet the problem head-on, I consider less direct strategies: these involve formulating functionalism or its causal claims in such a way that they appear not to generate the problem of metaphysically necessary effects. I argue against these indirect solutions, in each case concluding either that the problem still arises or that avoiding it requires the adoption of an unorthodox form of functionalism (itself a surprising result). In the final 2 section, I advocate a more straightforward solution to the problem: Because of the backward-looking manner in which causal-historical theories characterize mental properties, they are not subject to any version of the problem of metaphysically necessary effects, and this constitutes a reason to favor such theories over conceptual-or functional-role accounts of mental properties. II. Functionalism and metaphysically necessary effects Let us begin with an attempt simply to see how mental properties and their instantiations could fit into a material universe, absent a reduction of mental properties or states to physical ones, and how they might so fit in a way that allows for genuine mental causation. According to one prominent physicalist view, token physicalism, every event (or state—let this be understood hereafter) is a physical event, in the …