Online research in philosophy

Nonreductive physicalism provides an appealing solution to the nature of mental properties. But its success as a theory of mental properties has been called into doubt by claims that it cannot adequately handle the problems of mental causation, as it leads either to epiphenomenalism or to thoroughgoing overdetermination. I argue that these apparent problems for the nonreductivist are based in fundamental confusion about causation and explanation. I distinguish two different types of explanation and two different relations to which they appeal: causation and determination. I argue that these types of explanation do not compete with one another, nor do these relations jointly result in overdetermination. In closing I develop a nonreductivist solution to mental causation which avoids both the hazards of epiphenomenalism and of overdetermination and so demonstrates a way to save nonreductive physicalism from the problems of mental causation.

The realization relation that allegedly holds between mental and physical properties plays a crucial role for so-called non-reductive physicalism because it is supposed to secure both the ontological autonomy of mental properties and, despite their irreducibility, their ability to make a causal difference to the course of the causally closed physical world. For a long time however, the nature of realization has largely been ignored in the philosophy of mind until a couple of years ago authors like Carl Gillett, Derk Pereboom, or Sydney Shoemaker proposed accounts according to which realization is understood against the background of the so-called ‘causal theory of properties’. At least partially, the hope was to solve the problem of mental causation, in particular the kind of causal exclusion reasoning made famous by Jaegwon Kim, in a way acceptable to non-reductive physicalists. The paper asks whether a proper explication of the realization relation can indeed help explain how physically realized mental properties can be causally efficacious in the causally closed physical world and argues for a negative answer: it is important for the non-reductive physicalist to understand what exactly the realization relation amounts to, but it does not solve the problem of mental causation.

Argument for Epiphenomenalism [I]: (A) Mental event-tokens are identical with physical event-tokens. (B) The causal powers of a physical event are determined only by its physical properties; and (C) mental properties are not reducible to physical properties.

The paper argues for four claims: (1) The problem of mental causation and the argument for its solution in terms of the identity of mental with physical causes are independent of the theory of causation one favours. (2) If one considers our experience of agency as described by folk psychology to be veridical, one is committed to an anti-Humean metaphysics of causation in terms of powers that establish necessary connections. The same goes for functional properties in general. (3) A metaphysics of causation in terms of powers is compatible with physics. (4) If combined with the argument for mental causes being identical with physical causes, that metaphysics leads to a conservative reductionism.

Stephen Yablo has recently argued for a novel solution to the mental causation problem: the mental is related to the physical as determinables are related to determinates; determinables are not causal rivals with their determinates; so the mental and the physical are not causal rivals. Despite its attractions the suggestion seems hard to accept. In this paper I develop the idea that mental properties and physical properties are not causal rivals. Start with property dualism, supervenience, multiple realizability, and the claim that no more than one supervenience base for a mental property can be had by a single instance of the mental property. Then a probabilistic account of causation will be unable to certify either mental properties or physical properties as causal factors for effect types. I suggest that this shows that we should not count mental properties as causal rivals with physical properties.

Sydney Shoemaker has proposed a new definition of `realization’ and used it to try to explain how mental events can be causes within the framework of a non-reductive physicalism. I argue that it is not actually his notion of realization that is doing the work in his account of mental causation, but rather the assumption that certain physical properties entail mental properties that do not entail them. I also point out how his account relies on certain other controversial assumptions, including analytical filler-functionalism for mental properties, and the assumption that causes must be proportional to their effects. I conclude by pointing out that Shoemaker has provided no explanation of why, on his view, certain physical properties entail mental properties.

Sydney Shoemaker has attempted to save mental causation by a new account of realization. As Brian McLaughlin argues convincingly, the account has to face two major problems. First, realization does not guarantee entailment. So even if mental properties are realized by physical properties, they need not be entailed by them. This is the first, rather general metaphysical problem. A second problem, which relates more directly to mental causation is that Shoemaker must appeal to some kind of proportionality as a constraint on causation in order to avoid redundant mental causation. I argue that, in addition, a “piling problem” arises, since causal powers seem to be bestowed twice. Then, I try to sketch an alternative view of the relation between causal powers and properties—a reductionist view—which fares better on some accounts. But it may have to face another and, perhaps, serious problem, the “problem of the natural unity of properties”. Finally, I will pose a question about the relation between causal powers and causation.

Yablo suggests that we can understand the possibility of mental causation by supposing that mental properties determine physical properties, in the classic sense of determination according to which red determines scarlet. Determinates and their determinables do not compete for causal relevance, so if mental and physical properties are related as determinable and determinates, they should not compete for causal relevance either. I argue that this solution won''t work. I first construct a more adequate account of determination than that provided by Yablo. I then consider two common accounts of the mental, token identity theories and dispositional theories, and argue that on neither do mental and physical properties satisfy the requirements for determination.

How can mental properties bring about physical effects, as they seem to do, given that the physical realizers of the mental goings-on are already sufficient to cause these effects? This question gives rise to the problem of mental causation (MC) and its associated threats of causal overdetermination, mental causal exclusion, and mental causal irrelevance. Some (e.g., Cynthia and Graham Macdonald, and Stephen Yablo) have suggested that understanding mental-physical realization in terms of the determinable/determinate relation (henceforth, 'determination') provides the key to solving the problem of MC: if mental properties are determinables of their physical realizers, then (since determinables and determinates are distinct, yet don't causally compete) all three threats may be avoided. Not everyone agrees that determination can do this good work, however. Some (e.g., Douglas Ehring, Eric Funkhauser, and Sven Walter) object that mental-physical realization can't be determination, since such realization lacks one or other characteristic feature of determination. I argue that on a proper understanding of the features of determination key to solving the problem of MC these arguments can be resisted.