Fodor on multiple realizability and nonreductive physicalism: Why the argument does not work

This paper assesses Fodor’s well-known argument from multiple realizability to nonreductive physicalism. Recent work has brought out that the empirical case for cross-species multiple realizability is weak at best and so we consider whether the argument can be rebooted using a “thin” notion of intra-species multiple realizability, taking individual neural firing patterns to be the realizers of mental events. We agree that there are no prospects for reducing mental events to individual neural firing patterns. But there are more plausible candidates for the neural realizers of mental events out there, namely, global neural properties such as the average firing rates of neural populations, or the local field potential. The problem for Fodor’s argument is that those global neural properties point towards reductive versions of physicalism.

Two Kinds of High-Level Probability

According to influential views the probabilities in classical statistical mechanics and other special sciences are objective chances, although the underlying mechanical theory is deterministic, since the deterministic low level is inadmissible or unavailable from the high level. Here two intuitions pull in opposite directions: One intuition is that if the world is deterministic, probability can only express subjective ignorance. The other intuition is that probability of high-level phenomena, especially thermodynamic ones, is dictated by the state of affairs in the world. We argue in support of this second intuition and we show that in fact there are two different ways in which high-level probability describes matters of fact, even if the underlying microscopic reality is deterministic. Our analysis is novel, but supports approaches by, e.g., Loewer, Albert, Frigg and Hoefer, List and Pivato. In particular, the reductive view we propose here can be seen as a naturalization of the above approaches. We consider consequences of our result for nonreductive physicalist approaches, such as functionalism, that admit multiple realization of the kinds that appear in the special sciences by physical kinds. We show that nonreductive physicalism implies the existence of nonphysical matters of fact.

Nonreductive Physicalism and Mental Causation

In this work I articulate and defend a problem about the place of the mind in the causation of behaviour. Ask why someone did a certain action and you can see the problem arise, if only you assume certain plausible suppositions about the world. The suppositions are taken to be those of nonreductive materialism.I think that the argument from exclusion, originally developed by Jaegwon Kim, shows that unless there is overdetermination, the mental cannot be causally relevant in the causation of behaviour. It is my view, however, that a proper understanding of overdetermination shows that the overdetermination move is not available to the nonreductive physicalist. That is, he cannot escape exclusion by claiming that the mental overdetermines the physical in the causation of our actions.It is argued that neither appeals to economy nor to Bennett's counterfactual test are good ways to decide matters of overdetermination. That should be decided in terms of the ability of a theory to consistently permit such overdetermination, which however is shown not to be the case for nonreductive materialism.Moreover, in general all realized properties will face this problem - assuming them to be causally relevant will ignite exclusionary claims and in the competition for relevance, physical properties will have a better and more fundamental claim for relevance, threatening once again to relegate realized properties to the category of epiphenomena.

Nonreductive Physicalism and Mental Causation

I want now to consider what the correct way to understand overdetermination could tell us about the exclusion problem. But what is a better understanding of overdetermination? I think the following example, to be understood as a counterexample to Bennett's test, can lead the way.