Online research in philosophy

2. The Contingency and A posteriority Constraint: A formulation of the thesis must make physicalism come out contingent and a posteriori. First, physicalism is a contingent truth, if it is a truth. This means that physicalism could have been false, i.e. there are counterfactual worlds in which physicalism is false, for example, counterfactual worlds in which there are <span class='Hi'>miracle</span>-performing angels.[9] Moreover, if physicalism is true, our knowledge of its truth is a posteriori. This is to say that there are ways the world could turn out to be such that physicalism is false. For example, if there are <span class='Hi'>miracle</span>-performing angels, then physicalism is false. So there are worlds considered as actual in which physicalism is false.[10] For short, call this ‘the a posteriority constraint’.[11].

Mary is confined to a black-and-white room, is educated through black-and-white books and through lectures relayed on black-and white television. In this way she learns everything there is to know about the physical nature of the world. She knows all the physical facts about us and our environment, in a wide sense of 'physical' which includes everything in completed physics, chemistry, and neurophysiology, and all there is to know about the causal and relational facts consequent upon all this, including of course functional roles. If physicalism is true, she knows all there is to know. For to suppose otherwise is to suppose that there is more to know than every physical fact, and that is just what physicalism denies. … It seems, however, that Mary does not know all there is to know. For when she is let out of the black-and- white room or given a color television, she will learn what it is like to see something red, say. This is rightly described as learning—she will not say “ho, hum.” Hence, physicalism is false. (Jackson 1986, p. 291, Chapter 2, this volume).

The conclusion of this argument (hereafter ZA) entails the falsity of physicalism because, technical details aside, physicalism is or entails the thesis that every psychological truth is entailed by some physical truth. If it is possible that I have a zombie duplicate however, then it is possible that the physical truths are as they are and some psychological truth is different. Hence 3 entails that physicalism is false. The second conceivability argument is one that is almost as famous, though perhaps it is less famous for being a conceivability argument: the perfect actor argument against behaviorism (see, e.g., Putnam 1963, 1975). In a version that is both familiar and relatively clear, it goes like this.

The distinction between token and type physicalism is a familiar feature of discussion of psychophysical relations. Token physicalism, or ontological physicalism, is the view that every token, or particular, in the spatiotemporal world is a physical particular. It is contrasted with type physicalism, or property physicalism -- the view that every first-order type, or property, instantiated in the spatiotemporal world is a physical property. Token physicalism is commonly viewed as a clear thesis, strictly weaker than property physicalism, strictly stronger than substance physicalism, and as a good statement on its own or in conjunction with other theses of minimal physicalism.[i] It is also generally simply assumed to be true, though Davidson has offered a famous argument for its truth, and some have argued against it. Many of those arguing against it are substance physicalists, indicating that they believe token physicalism to be a strictly stronger view.[ii].

A number of philosophers think that, while we cannot explain how the mind is physical, we can know that it is physical, nonetheless. That is, they accept both the explanatory gap between the mental and the physical and ontological physicalism. I argue that this position is unstable. Among other things, I argue that once one accepts the explanatory gap, the main argument for ontological physicalism, the argument from causation, looses its force. For if one takes physical/nonphysical causation and ontological physicalism to be equally mysterious, as physicalists who accept the explanatory gap are inclined to do, there is little justification for accepting ontological physicalism rather than rejecting the causal closure of the physical.

Any position that promises genuine progress on the mind-body problem deserves attention. Recently, Daniel Stoljar has identified a physicalist version of Russells notion of neutral monism; he elegantly argues that with this type of physicalism it is possible to disambiguate on the notion of physicalism in such a way that the problem is resolved. The further issue then arises of whether we have reason to believe that this type of physicalism is in fact true. Ultimately, one needs to argue for this position by inference to the best explanation, and I show that this new type of physicalism does not hold promise of more explanatory prowess than its relevant rivals, and that, whether it is better than its rivals or not, it is doubtful whether it would furnish us with genuine explanations of the phenomenal at all.

What has come to be known as “a priori physicalism” is the thesis, roughly, that the non-physical truths in the actual world can be deduced a priori from a complete physical description of the actual world. To many contemporary philosophers, a priori physicalism seems extremely implausible. In this paper I distinguish two kinds of a priori physicalism. One sort – strict a priori physicalism – I reject as both unmotivated and implausible. The other sort – liberal a priori physicalism – I argue is both motivated and plausible. This variety of a priori physicalism insists that the necessitation of non-physical truths by the physical facts must be underwritten in a certain fashion by a priori knowledge, but the a priori knowledge need not amount to a simple deduction of the non-physical truths from a complete physical description of the world. Further, this sort of liberal a priori physicalism has the advantage that it offers hope for a genuinely satisfying account of how the physical facts manage to necessitate the facts about phenomenal consciousness – thereby in effect solving the “hard problem” of consciousness. The first half of the paper sets out the motivation for liberal a priori physicalism and its superiority to the strict version; the second half presents one strategy available to the liberal a priori physicalist for showing how consciousness can be accommodated in a purely physical world.

Perhaps more controversial than whether physicalism is true is what exactly would have to be true for physicalism to be true. Everyone agrees that, intuitively at least, physicalism is the thesis that there is nothing over and above the physical. The disagreements arise in how to get beyond this intuitive formulation. Until about ten years ago, participants in this debate were concerned primarily with answering two questions. First, what is it for a property, kind, relation, or individual to be a physical one?

Physicalism is the claim that that there is nothing in the world but the physical. Philosophers who defend physicalism have to confront a well-known dilemma, known as Hempel’s dilemma, concerning the definition of ‘the physical’: if ‘the physical’ is whatever current physics says there is, then physicalism is most probably false; but if ‘the physical’ is whatever the true theory of physics would say that there is, we have that physicalism is vacuous and runs the risk of becoming trivial. This article has two parts. The first, negative, part is devoted to developing a criticism of the so-called via negativa response to Hempel’s dilemma. In the second, more substantial, part, I propose to take the first horn of Hempel’s dilemma. However, I argue for a broad construal of ‘current physics’ and characterize ‘the physical’ accordingly. The virtues of the broad characterization of ‘the physical’ are: first, it makes physicalism less likely to be false; and second, it ties our understanding of ‘the physical’ to the reasons we have for believing in physicalism. That is, it fulfills the desideratum of construing our theses according to the reasons we have to believe in them.

The debate over physicalism in philosophy of mind can be seen as concerning an inconsistent tetrad of theses: (1) if physicalism is true, a priori physicalism is true; (2) a priori physicalism is false; (3) if physicalism is false, epiphenomenalism is true; (4) epiphenomenalism is false. This paper argues that one may resolve the debate by distinguishing two conceptions of the physical: on the theory-based conception, it is plausible that (2) is true and (3) is false; on the object-based conception, it is plausible that (3) is true and (2) is false. The paper also defends and explores the version of physicalism that results from this strategy.