Online research in philosophy

This paper is about the causal exclusion argument against non-reductive physicalism. Many philosophers think that this argument poses a serious problem for non-reductive theories of the mind — some think that it is decisive against them. In the first part I will outline non-reductive physicalism and the exclusion argument. Then I will distinguish between three versions of the argument that address three different versions of non-reductive physicalism. According to the first, the relation between mental and physical events is token-identity. According to the second, mental events are distinct from physical events, but the latter metaphysically include and determine the former. And on the third version, mental and physical events are entirely distinct. I will argue that the causal exclusion argument is not decisive against non-reductive physicalism in any of the three versions. According to non-reductive physicalism, mental events are dependent on physical events. Causal exclusion and overdetermination, however, requires distinct and independent causes. I will argue that the burden of proof lies with the opponents of non-reductive physicalism, who have to explain how metaphysically dependent events can possibly overdetermine an effect or exclude each other from being causally efficacious.

Over the past few decades, Jaegwon Kim has argued that non-reductive physicalism is an inherently unstable position. In his view, the most serious problem is that non-reductive physicalism leads to type epiphenomenalism—the causal inefficacy of mental properties. Kim suggests that we can salvage mental causation by endorsing functional reduction. Given the fact that Kim’s goal in formulating functional reduction is to provide a robust account of mental causation it would be surprising if his position implies eliminativism about mental properties or leads to a view that is similar to one of the versions of non-reductive physicalism that he criticizes. We will show that depending on how certain key claims are interpreted, there are reasons for thinking functional reduction has these implications, in which case either Kim fails to provide a robust account of mental causation or there is reason to suspect that some of his criticisms of non-reductive physicalism are misguided.

Semifactuals and Epiphenomenalism

Mental properties are said to be epiphenomenal because they do not pass the counterfactual test of causal relevance. Jacob (1996) adopts the defence of causal efficacy of mental properties developed by LePore and Loewer (1987). They claim that those who argue for the epiphenomenalism of the mental place too strong a requirement on causal relevance, which excludes causally efficacious properties. Given a proper analysis of causal relevance, the causal efficacy of mental properties is saved. I defend the counterfactual test and epiphenomenalism of the mental against this critique. In causal counterfactuals we hold everything the same, take out the causal property and see if the effect property occurs. We do not replace the causal property with a barely different property as presupposed by LePore and Loewer. But I recognize some general problems in making counterfactual claims about mental events, which raise doubts about the usefulness of the counterfactual test in general.

A well-known ``overdetermination''argument aims to show that the possibility of mental causes of physical events in a causally closed physical world and the possibility of causally relevant mental properties are both problematic. In the first part of this paper, I extend an identity reply that has been given to the first problem to a property-instance account of causal relata. In the second, I argue that mental types are composed of physical types and, as a consequence, both mental and physical types may be causally relevant with respect to the same physical effect, contrary to the overdetermination argument. In further sections, I argue that mental types have causal powers, consider some objections and reject an alternative version of part-whole physicalism. Throughout I assume that causal relata are tropes and property types are classes of tropes.

Recent discussions of mental causation have focused on three principles: (1) Mental properties are (sometimes) causally relevant to physical effects; (2) mental properties are not physical properties; (3) every physical event has in its causal history only physical events and physical properties. Since these principles seem to be inconsistent, solutions have focused on rejecting one or more of them. But I argue that, in spite of appearances, (1)–(3) are not inconsistent. The reason is that 'properties' is used in different senses in the principles. In (1) and (3), 'properties' should be read as 'tropes' (properties here are particulars), while in (2) 'properties' should read as 'types' (properties here are universals or classes). Although mental types are distinct from physical types, every mental trope is a physical trope. This allows mental properties to be causally relevant to physical effects without violating the closed character of the physical world.

This paper is an attempt to understand the content of, and motivation for, a popular form of physicalism, which I call ‘non-reductive physicalism’. Non-reductive physicalism claims although the mind is physical (in some sense), mental properties are nonetheless not identical to (or reducible to) physical properties. This suggests that mental properties are, in earlier terminology, ‘emergent properties’ of physical entities. Yet many non-reductive physicalists have denied this. In what follows, I examine their denial, and I argue that on a plausible understanding of what ‘emergent’ means, the denial is indefensible: non-reductive physicalism is committed to mental properties being emergent properties. It follows that the problems for emergentism—especially the problems of mental causation—are also problems for non-reductive physicalism, and they are problems for the same reason.

It has been argued that nonreductive physicalism leads to epiphenominalism about mental properties: the view that mental events cannot cause behavioral effects by virtue of their mental properties. Recently, attempts have been made to develop accounts of causal relevance for irreducible properties to show that mental properties need not be epiphenomenal. In this paper, I primarily discuss the account of Frank Jackson and Philip Pettit. I show how it can be developed to meet several obvious objections and to capture our intuitive conception of degrees of causal relevance. However, I argue that the account requires large-scale miraculous coincidence for there to be causally relevant mental properties. I also argue that the same problem arises for two apparently very different accounts of causal relevance. I suggest that this result does not show that these accounts, on appropriate readings, are false. Therefore, I tentatively conclude that we have reason to believe that irreducible mental properties are causally irrelevant. Moreover, given that there is at leastprima facie evidence that mental properties can be causally relevant, my conclusion casts doubt on nonreductive physicalist theories of mental properties.

Frank Jackson and Philip Pettit have defended a non-reductive account of causal relevance known as the ‘program explanation account’. Allegedly, irreducible mental properties can be causally relevant in virtue of figuring in non-redundant program explanations which convey information not conveyed by explanations in terms of the physical properties that actually do the ‘causal work’. I argue that none of the possible ways to spell out the intuitively plausible idea of a program explanation serves its purpose, viz., defends non-reductive physicalism against Jaegwon Kim’s Causal Exclusion Argument according to which non-reductive physicalism is committed to epiphenomenalism because irreducible mental properties are ‘screened off’ from causal relevance by their physical realizers. Jackson and Pettit’s most promising explication of a program explanation appeals to the idea of invariance of effect under variation of realization , but I show that invariance of effect under variation of realization is neither necessary nor sufficient for causal relevance.

Physicalist epiphenomenalism is the conjunction of the doctrine that tokens of mental events are tokens of physical events and the doctrine that mental events do not exert causal powers by virtue of falling under mental types. The purpose of the paper is to show that physicalist epiphenomenalism, contrary to what many have thought, is not subject to the objections that have been raised against classic epiphenomenalism. This is argued with respect to five such objections: that introspection shows that our mental properties are causally efficacious; that concrete existents and their properties necessarily possess causal powers; that the explanatory and predictive success of psychology implies that psychological properties exist and are causally efficacious; that epiphenomenalism cannot deal with the other minds problem, and that it is unlikely that our mentality does not endow us with evolutionary advantages and therefore it is unlikely that mental properties are not causally efficacious.

This paper argues that the non-reductive monist need not be concerned about the ‘problem’ of mental causation; one can accept both the irreducibility of mental properties to physical properties and the causal closure of the physical. More precisely, it is argued that instances of mental properties can be causally efficacious, and that there is no special barrier to seeing mental properties whose instances are causally efficacious as being causally relevant to the effects they help to bring about. It is then shown that the causal relevance of mental properties is consistent with there being no downward causation, so the dilemma of ‘epiphenomenalism or reduction’ can be avoided. Non-reductive monism lives on as a viable position in the philosophy of mind.