How should we define physicalism or minimal physicalism? In my view, this question calls for stipulation because these are theoretical terms without a uniform use. Different views of psychophysical relations are physicalistic in different ways and to different degrees, and there is an obvious interest in clarifying and distinguishing these views and determining which are true. My aim in this chapter will be to do some of the clarifying and distinguishing. Stipulation of a unique thesis as physicalism or minimal physicalism must come with a rationale, and as I have none to offer I shall not pursue this.

Some regard physicalism as the thesis that all first-order properties instantiated in the spatiotemporal world are physical properties. I shall refer to this as type physicalism or property physicalism. It can be presented in the form of a supervenience thesis – another popular way of defining physicalism – on the assumption that a property is physical if and only if it logically supervenes on microphysical properties. This is one way, or a first approximation of a way, of characterizing a physical property in terms of microphysical properties. But as I think that the following discussion will apply on any reasonable view of physical property, I will mostly continue to talk of physical properties without getting more specific. I shall assume that it will be clear enough to think of a microphysical property as an assignment of fundamental microphysical parameters in some type of spatial or spatiotemporal region, where the fundamental microphysical parameters are those featuring in an ultimate microphysical theory.

According to Jeffrey Poland, the “basic conviction” of the physicalist is that:

I agree with Poland that this sort of explanatory claim is central to the physicalist idea. In this chapter I explore how we may fill out and clarify that explanatory claim in terms of its modal implications. In particular, I focus on two sufficiency claims to which physicalism is committed. Ultimately, there is no way to replace the explanatory claim with sufficiency claims; nonetheless, there are good reasons to focus on them. They help cash out the demands of physicalism, giving us a better grasp on its content. In so doing, they also put us in a better position to evaluate apparent counterexamples to physicalism, think further about the implications of physicalism for science, and, perhaps most urgently, get clear on what sense there is to be made of so-called naturalization projects. Further, they provide a dialectically useful route to justifying physicalism itself. As I shall argue at the end of this chapter, if they are true, it is overwhelmingly likely that the overarching explanatory claim is true.

Physicalistic Explanation and Sufficiency

In what sense is the physical realm supposed to explain everything else?

Every era has its weltanschauung and in much contemporary philosophy the doctrine of ‘physicalism’ plays this role. Such foundational assumptions exert considerable influence by subtly configuring philosophical debates, problems, and projects, though the precise nature of these assumptions is often hard to clearly discern. Happily, however, philosophers have recently begun to subject physicalism to sustained scrutiny, both positive and negative. Exactly how the doctrine of physicalism should be formulated, what its significance is, and whether it has a justification, in addition to a range of other issues, have all recently been discussed.

We believe such attention is intellectually a very healthy development. There are always parts of the reigning weltanschauung that it would be productive to discard and those that ought to be retained. But this process of critically evaluating various assumptions only proceeds in lockstep with the illumination of their natures. The present anthology was conceived with these thoughts in mind and the chapters that follow all seek to further the project of critically illuminating various aspects of physicalism and its implications. Though we shall let the authors speak for themselves, and the variety of their concerns precludes easy summary, it may help the reader to have a general guide to the volume's contents. The largest section, “Part 1, Physicalism,” comprises chapters generally sympathetic to the doctrine of physicalism. Among the work they undertake, is that of articulating the historical genesis and present justification of physicalism; its most adequate formulation; modal status; and its implications for mental causation and the special sciences. A range of more or less critical chapters comprise the next section, “Part 2, Physicalist Discontents,” and take as their focus the metaphysical presuppositions of physicalism, …

Humans live in quotidian contexts. We plan trips, cook meals, and do the wash. Our time is spent within narrow boundary conditions. Our thought needn't stray from the commonplace. Our expectation needn't stray from everyday possibility. For this reason, we're disposed to mistake the contours of quotidian possibility for those of intelligibility. Yet the resulting bias is a kind of modal tunnel vision. We overlook certain conceptual possibilities. We discharge others due to their alien face alone.

In this note, I locate four features of everyday life. They generate blinkered expectation that large builds from small without remainder. I note they're contingent features of reality at best, discuss how they might fail, and use that discussion to unearth quotidian bias in two spots. First, I claim the stock argument for physicalism rests on unsound presuppositions induced by everyday life; second, I claim the stock expression of physicalism is modally misguided due to such presupposition as well.

The Roots

Everyday life renders common sense reductively oriented. There are four reasons why. Three are widely recognized. The fourth is not.

1. (A) In quotidian contexts: the large is the small writ big, and the small is the large writ small. Conceptually identical phenomena appear on different levels of scale. For instance: large-scale objects have shape, and so do their smaller cousins; large-scale objects have color, and so do their smaller cousins; large-scale objects move, and so do their smaller cousins. Differences across level are not differences of type. They are differences of scale alone. One range of concepts is apt for both levels. Large and small are conceptually homogenous (LASCH).

2. […]

Let a conceivability argument be any argument that aims to refute physicalism by showing that some claim that physicalism must treat as necessary is not in fact necessary because its negation is conceivable and hence genuinely possible. According to conceivability arguments in the recent tradition, it is conceivable that so-and-so iff the thought that so-and-so can be entertained without explicit contradiction or the sense of conceptual blockage one has (albeit to an unusually intense degree) in attempting to entertain the negation of the claim that two is a number. According to such arguments, the claim that it is assumed physicalism must treat as necessary is a certain more or less immediate consequence of any physicalist type-identity claim whereby some nonphysical property – some property expressible in nonphysical vocabulary – is identified with either a physical property or a physically realized functional property. So suppose the (nonphysical) property of being N is identified with the (physical or functional) property of being P. Then, on the assumption that the identity statement is formed using rigid designators and that such identity statements are necessary, it follows that, necessarily, an object is N iff it is P. But if, as the argument claims, it is conceivable, and hence possible, that something should be N but not P (or P but not N), then it is false that, necessarily, an object is N iff it is P, and hence false that being N just is being P.

But traditional conceivability arguments of this sort fail. Even though it is surely conceivable, in the sense specified, that something should be N but not P, the real possibility that something should be N but not P just does not follow.

It is fairly widely believed that felt bodily sensations (aches, pains, itches, tickles, throbs, cramps, chills, and the like) have physical or at least functional correlates. That is to say, the following thesis is fairly widely believed:

The Correlation Thesis, if it is true, would not, of course, solve the mind-body problem for sensations. For the Correlation Thesis is compatible with virtually every theory of mind: not only with noneliminativist materialism and functionalism, but also with Cartesian Dualism, dual-aspect theory, neutral monism, and panpsychism.

Some philosophers, however, myself included, maintain that the following thesis would offer the best explanation of the correlation thesis:

This thesis implies the Correlation Thesis. For, as Saul Kripke (1971) demonstrated,

The kind of necessity in question is the strongest sort: if A = B, then there is, unqualifiedly, no way the world could be such that A is not identical with B. Thus, given the necessity of identity, if the Type Identity Thesis is true, then the Correlation Thesis is true as well.

The conclusion I aim to establish in this chapter is this: the solution to the mind-body problem cannot take the form of an empirical identity statement but must rather consist in an analytic identity statement. That is, to solve the problem we would need to provide a conceptual reduction of consciousness, not an a posteriori reduction. It is not that I know what this conceptual reduction would look like – far from it. My thesis is merely that there is a general argument that shows that the solution must take this form. I shall also be concerned to spell out the consequences of this thesis for the prospects of solving the mind-body problem, and to indicate how my conclusion bears upon certain arguments that have been given to undermine physicalism.

The logical analysis of identity statements has proved crucial in assessing the claims of physicalism, and so it will be in this chapter. Early identity theorists, notably J.J.C. Smart, observed that not all true identity statements are conceptual truths, following Frege's precedent. This opened the way to claiming that there might be true identity statements linking mental and physical properties that could not be certified to be true on conceptual grounds alone. It was thus not incumbent on a physicalist to provide any analysis of mental concepts in order to claim to possess a complete physical reduction of mental properties. This liberalization of the conditions of adequacy upon a physicalist theory brightened the prospects for that theory considerably, and it established a paradigm for what a solution to the mind-body problem might look like. We could say that pain is C-fiber stimulation in the same spirit in which we say that heat is molecular motion.

Substantial progress has been made working out the metaphysics underlying physicalism (P) and its idea that everything is, in some sense, physical. But its proponents have not confined themselves to metaphysical claims and have also argued that physicalism has an important methodological role. Hartry Field, Jeffrey Poland, and W.V.O. Quine, among others, all defend what I will call Methodological Physicalism (MP), the position that we should use a Physicalist Criterion under which P is used to assess our theories. Methodological Physicalism exerts considerable philosophical influence. Vindicatory ‘naturalization’ projects, for example, are apparently based upon implicit acceptance of MP. Theories that posit intentional states, moral properties such as goodness and the right, and mathematical entities such as sets and numbers, have all been argued to be in danger of abandonment, and in consequent need of naturalization, because they fail a Physicalist Criterion.

The prescriptions of MP are clearly substantive and an obvious question is how use of a Physicalist Criterion is justified. Any such justification must be compatible with the broadly ‘naturalistic’ orientation of defenders of MP who consequently look to the sciences. For example, Harty Field (1972), and also Jeffrey Poland (1994), both offer what I will call the Justification from Scientific Practice (JSP) to defend their use of a Physicalist Criterion. This justification of MP has as its first premise some version of the normative position that we ought to use in all areas of empirical inquiry the methods that have been successfully used in sciences, and a second, descriptive premise that the Physicalist Criterion has been successfully used to appraise scientific theories in a variety of historical cases.

Mental Causation and Consciousness

Schopenhauer famously called the mind-body problem a “world-knot,” or “Weltknoten,” and he was surely right. However, the mind-body problem is not really a single problem; it is a cluster of connected problems about the relationship between mind and matter. What these problems are depends, of course, on a broader framework of philosophical and scientific assumptions and presumptions in which the questions are posed and potential solutions are formulated. For the contemporary physicalist, I believe that there are two problems that truly make the mind-body problem a Weltknoten, an intractable and perhaps ultimately insoluble puzzle. These problems concern mental causation and consciousness. The problem of mental causation is to answer this question: How can the mind exert its causal powers in a world that is fundamentally material? The second problem, that of consciousness, is to answer the following question: How can there be such a thing as a mind, or consciousness, in a material world? Moreover, as I will argue, the two problems are interconnected – the two knots are intertwined, and this makes it all the more difficult to unsnarl either of them.

Giving an account of mental causation has been, for the past three decades, one of the main preoccupations of philosophers of mind who are committed to physicalism in one form or another. The problem, of course, is not new: As every student of western philosophy knows, Descartes, who arguably invented the mind-body problem, was confronted forcefully by his contemporaries on this issue. But this does not mean that Descartes's problem is our problem.

Introduction

Hilary Putnam explains that:

Materialism says that all facts, in particular all mental facts, obtain in virtue of the spatiotemporal distribution, and properties, of matter. It was, as Putnam says, “metaphysics within the bounds of science,” but only so long as science was thought to say that the world is made out of matter. In this century physicists have learned that there is more in the world than matter and, in any case, matter isn't quite what it seemed to be. For this reason many philosophers who think that metaphysics should be informed by science advocate physicalism in place of materialism. Physicalism claims that all facts obtain in virtue of the distribution of the fundamental entities and properties – whatever they turn out to be – of completed fundamental physics.

The enterprise of fundamental physics can be characterized (perhaps a little tendentiously) in terms of its ambition and the kinds of concepts it employs in attempting to satisfy that ambition. The goal of physics is, first, to discover the laws that govern or describe the motions of macroscopic material objects; and second, to discover laws that are complete in that they completely account for every event mentioned by those laws.

Introduction

In this chapter I want to discuss the way in which physical science has come to claim a particular kind of hegemony over other subjects in the second half of this century. This claim to hegemony is generally known by the name of physicalism. In this chapter I shall try to understand why this doctrine has come to prominence in recent decades. By placing this doctrine in a historical context, we will be better able to appreciate its strengths and weaknesses.

As a preliminary, note that contemporary physicalism is an ontological rather than a methodological doctrine. It claims that everything is physically constituted, not that everything should be studied by the methods used in physical science. This emphasis on ontology rather than methodology marks a striking contrast with the ‘unity of science’ doctrines prevalent among logical positivists in the first half of the century. The logical positivists were much exercised by the question of whether the different branches of science, from physics to psychology, should all use the same method of controlled observation and systematic generalization. They paid little or no attention to the question of whether everything is made of the same physical stuff.

By contrast, physicalism, as it is understood today, has no direct methodological implications. Some physicalists uphold the view that all sciences should use the “positivist” methods of observation and generalization.

In the first post World War II identity theories (e.g., Place [1956], Smart [1962]), mind-brain identities were held to be contingent. However, in work beginning in the late 1960s, Saul Kripke ([1971], [1980]) convinced the philosophical community that true identity statements involving names and natural kind terms are necessarily true and, furthermore, that many such necessary identities can only be known a posteriori. Kripke also offered an explanation of the a posteriori nature of ordinary theoretical identities such as that water = H2O. We identify the kinds and substances involved in theoretical identities by certain of their contingent properties. What we discover when we discover a theoretical identity is the underlying nature of the kind that we identify by those contingent properties.

Now, of course, it was being a posteriori, not being contingent, that mattered to the identity theorists anyway, so the necessity of identity is not, in itself, damaging to mind-brain identity theories. However, Kripke also argued persuasively that the alleged mind-brain identities could not be treated in the same way as ordinary theoretical identities. We “identify” pain by feeling it, and surely how it feels is an essential property of pain, not a contingent property. Thus, a mind-body identity theory must provide a different explanation of why its identities are a posteriori.

A new wave of materialists has appeared on the scene with a new strategy for explaining the a posteriori nature of its alleged identities. The strategy is to locate the explanation for the a posteriori nature of mind-body identities, not on the side of the world, but on the side of the mind – in different ways of thinking about or imagining, or in different concepts.

Introduction

There has been considerable worry for the last thirty years about the causal efficacy of the mental: How, given the closure of physics and the apparent “irreducibility” of the mental to the physical, can mental phenomena play any causal/explanatory role in the world? Aren't they mere “epiphenomena”? In reaction to these worries, Tyler Burge (1993) has reasonably argued that:

And Lynn Rudder Baker (1993) has rightly suggested that we:

Baker and Burge are applying the sensible point, suggested years ago by Moore and emphasized by Quine (1953a), that there seems to be no specially privileged position outside of common sense and science from which philosophers can effectively dismiss them. It would take a pretty powerful metaphysical argument indeed to give us reason to give up our belief in familiar forms of mental causation.

For all the wisdom of this position, however, I fear that Burge overstates the case in a crucial way. The problem of “epiphenomenalism” that many of these “metaphysical” discussions have been addressing arises in part from the difficulty of specifying a mechanism linking the mental and the physical.

The problem of mental causation is at the heart of the mind-body problem. And for physicalist or materialist views of mind, the key to solving the problem of mental causation is getting a satisfactory understanding of how the mental is realized in the physical. Recent discussions of physicalism have focused on the notion of supervenience; but I think that the focus should instead be on the notion of realization. Supervenience comes in a variety of forms – and the form we need to understand, in order to understand mental causation, is that in which the properties in the supervenience base can be said to realize the properties that supervene on them. Any physicalist theory, whether or not it is a functionalist theory, needs to maintain that the mental is realized in the physical, and so needs an account of realization. But my main focus will be on the realization of functional properties.

I take as my point of departure a recent paper by George Bealer that attempts to show that functionalist accounts of mind cannot give a satisfactory account of self-consciousness. Although Bealer's primary target is functionalism, he takes his arguments to establish a version of property dualism. They are supposed to show that mental properties are “first-order properties,” not the higher-order properties functionalists take them to be. And because Bealer thinks that there are decisive reasons for rejecting type physicalism, he thinks that the only way for mental properties to be first order is for them to be nonphysical.