Tom Polger

The enduring metaphysical question about minds and mental phenomena concerns their nature. At least since Descartes this question—the mind-body problem—has been understood in terms of the viability or necessity of mind-body dualism, the thesis that minds and bodies are essentially distinct kinds of substance. Assuming that the nonmental (‘body’) portions of the world are constituted of physical stuff, the remaining question is: Are minds or mental phenomena essentially distinct non-physical substances, or phenomena that essentially involve such distinct kinds of substances? By the middle of the Twentieth Century there was broad philosophical and scientific consensus that the answer to this classical question about minds is negative: Minds and mental phenomena are not essentially distinct substances, nor are they phenomena that essentially involve distinct kinds of substances. There are at least two broad trends and one specific argument that lead to this conclusion. One trend is the decreasing influence of specifically theological arguments and commitments in philosophical argumentation, so that religious belief in immortal souls was no longer given much weight in the ontology of mind. The second trend, perhaps related to the first, is the increased demand that metaphysical theories bear explanatory fruits, so that the postulation of an immaterial and essentially mental substance appears to be a abdication from explanatory duties rather than a useful proposal. The argument, known to Descartes from the very beginning, is that there has never been an adequate account of 1 how two essentially distinct and incompatible substances could causally interact.1 Descartes’ solution was inadequate and brute, and his followers struggled with the problem—leading to Leibniz’s parallelism and Malebranche’s occasionalism, among other views. The problem of mental causation, then, is the central difficulty that underines substance dualism.2 The negative answer on the question of substance dualism, however, only increases the pressure for some monistic account of the nature of minds..

Consider what the brain-state theorist has to do to make good his claims. He has to specify a physical–chemical state such that any organism (not just a mammal) is in pain if and only if (a) it possesses a brain of suitable physical–chemical structure; and (b) its brain is in that physical–chemical state. This means that the physical–chemical state in question must be a possible state of a mammalian brain, a reptilian brain, a mollusc’s brain (octopuses are mollusca, and certainly feel pain), etc. At the same time, it must not be a possible (physically possible) state of the brain of any physically possible creature that cannot feel pain. Even if such a state can be found, it must be nomologically certain that it will also be a state of the brain of any extraterrestrial life that may be found that will be capable of feeling pain before we can even entertain the supposition that it may be pain. It is not altogether impossible that such a state will be found... . But this is certainly an ambitious hypothesis. (Putnam 1967/1975, p. 436) The belief that mental states are multiply realized is now nearly universal among philosophers, as is the belief that this fact decisively refutes the identity theory. I argue that the empirical support for multiple realization does not justify the confidence that has been placed in it. In order for multiple realization of mental states to be an objection to the identity theory, the neurological differences among pains, for example, must be such as to guarantee that they are of distinct neurological kinds. But the phenomena traditionally cited do not provide evidence of that sort of variation. In particular, examples of neural plasticity do not provide such evidence.

Fifty years ago J. J. C. Smart published his pioneering paper, “Sensations and Brain Processes.” It is appropriate to mark the golden anniversary of Smart’s publication by considering how well his article has stood up, and how well the identity theory itself has fared. In this paper I first revisit Smart’s text, reflecting on how it has weathered the years. Then I consider the status of the identity theory in current philosophical thinking, taking into account the objections and replies that Smart discussed as well as some that he did not anticipate. Finally, I offer a brief manifesto for the identity theory, providing a small list of the claims that I believe contemporary identity theorist should accept. As it turns out, these are more or less the ones that Smart defended fifty years ago.

Michael Tye has recently been a vocal defender of color realism or, as I shall call it, color objectivism. Objectivism about color is the view that color properties are identical to intrinsic physical properties of the surfaces of objects. Subjectivism about color is the denial of color objectivism. Objectivists argue that color claims must be taken at face value. In this paper I forego the usual bickering about whether there are surface reflectance properties that can be identified with colors as the objectivist theory requires. Supposing that some such properties could be found, I argue that if objectivism about color were correct it would have the unsavory consequence that we are rarely if ever right—perhaps never right—about the particular colors of particular things. So objectivism does not bear out common attribution of colors to the surfaces of things, after all.

Multiple realizability has recently attractedrenewed attention, for example Bickle, 1998;Bechtel and Mundale, 1999; Bechtel and McCauley,1999; Heil, 1999; and Sober, 1999. Many of thesewriters revisit the topic of multiplerealizability in order to show that someversion of a mind-brain identity theory isviable. Although there is much of value inthese recent explorations, they do not addressthe underlying intuitions that have vexedphilosophers of mind since Hilary Putnamintroduced the concern (1967). I argue that thestandard way of construing multiplerealizability is a much stronger claim thanthat of Putnam's intuition alone. I distinguishfour interpretations of the multiplerealizability intuition. Some commonformulations of multiple realizability arealmost certainly true, while others are not atall plausible. I argue that the plausible formsof multiple realizability do not impugn theprospects for a mind-brain Identity Theory.

To what degree must the brains and bodies of creatures with minds have to be similar to the brains and bodies of human beings? Since the late 1960’s, most philosophers and cognitive scientists have supposed that there a relatively few constraints on what sorts of brains and bodies can realize minds. It is widely believed that minds are multiply realizable. Of course there were always dissenters, and in recent years their grumbling has grown harder to dismiss. In The Mind Incarnate , Lawrence Shapiro provides the first book-length study of the multiple realizability thesis. Such an examination is long overdue, and Shapiro’s treatment is sure to set the standard for the budding debate

David Chalmers burst onto the philosophical scene in the mid-1990s with his work on consciousness, which awakened slumbering zombie arguments against physicalism and transformed the explanatory gap into the hard problem of consciousness. The distinction between hard and easy problems of consciousness became a central dogma of the movement. Chalmers’ influence in philosophy and consciousness studies is unquestionable. But enthusiasts of Chalmers’ work on consciousness may be excused for not fully appreciating his own justification for drawing the hard/easy distinction, or even exactly which distinction he is drawing. Consequently, it is not clear that the ‘Chalmers’ hard problem’ that has been widely influential is Chalmers’ ‘hard problem’ of consciousness. Chalmers’ ‘hard problem’ rests on, among other things: a methodological view about how philosophy—metaphysics, especially—ought to be conducted; a view about the requirements for explanation and reduction in philosophy and in the sciences; and a theory of the semantics of concepts.1 Although Chalmers writes that the present book is not intended as a foundation for his

The 1990’s, we’ve been told, were the decade of the brain. But without anyone announcing or declaring, much less deciding that it should be so, the 90’s were also a breakthrough decade for the study of consciousness. (Of course we think the two are related, but that is another matter altogether.) William G. Lycan leads the charge with his 1987 book Consciousness (MIT Press), and he has weighed-in again with Consciousness and Experience (1996, MIT Press). Together these two books put forth Lycan’s formidable view of consciousness, extending the theory of mind that he calls ‘homuncular functionalism.’ Roughly, Lycan’s view is that conscious beings are hierarchically composed intentional systems, whose representational powers are to be understood in terms of their biological function. In this review we will call the view ‘teleological functionalism’ or ‘teleofunctionalism’ – the homuncular part, for which Lycan and Daniel Dennett argued convincingly, is now so widely accepted that it fails to distinguish Lycan’s view from other versions of functionalism. This, by itself, is a testament to the importance of Lycan’s work.

Suppose that consciousness is a natural feature of biological organisms, and that it is a capacity or property or process that resides in a single organ. In that case there is a straightforward question about the consciousness organ, namely: How did the consciousness organ come to be formed and why is its presence maintained in those organisms that have it? Of course answering this question might be rather difficult, particularly if the consciousness organ is made of soft tissue that leaves at best indirect fossil records, or if it has been fixed in the populations for such a long time that there are few available examples of organisms that lack the consciousness organ on which to conduct comparative experiments. No doubt there are other confounding practical obstacles as well. But these are just the complications that face biologists and natural historians on a regular basis, and they do not reflect any special problems about the study of consciousness. This is just to say that if consciousness is a natural feature of biological organisms then its origins and history can be studied in the same manner as other features of the biological world. It’s a hard business, but biologists are pretty good at it

In Natural Minds Thomas Polger advocates, and defends, the philosophical theory that mind equals brain -- that sensations are brain processes -- and in doing so brings the mind-brain identity theory back into the philosophical debate about consciousness. The version of identity theory that Polger advocates holds that conscious processes, events, states, or properties are type- identical to biological processes, events, states, or properties -- a "tough-minded" account that maintains that minds are necessarily indentical to brains, a position held by few current identity theorists. Polger's approach to what William James called the "great blooming buzzing confusion" of consciousness begins with the idea that we need to know more about brains in order to understand consciousness fully, but recognizes that biology alone cannot provide the entire explanation. Natural Minds takes on issues from philosophy of mind, philosophy of science, and metaphysics, moving freely among them in its discussion.Polger begins by answering two major objections to identity theory -- Hilary Putnam's argument from multiple realizability and Saul Kripke's modal argument against mind-brain identity. He then offers a detailed account of functionalism and functional realization, which offer the most serious obstacle to consideration of identity theory. Polger argues that identity theory can itself satisfy the kind of explanatory demands that are often believed to favor functionalism.

Saying that psychological states are functional states, the functionalist claims more than that psychological states have functions. Rather, functionalism is the theory that psychological states are defined and constituted by their functions. On this view, what it is to be a psychological state of a certain sort just is and consists entirely of having a certain function. Anything that has that function in a suitable system would therefore be that psychological state. If storing information for later use is the essential function of memory, then anything that has that function counts as a memory. Similarly, one might say that anything that traps or kills mice counts as a mouse trap

There is an argument for functionalism—and _ipso facto_ against identity theory—that can be sketched as follows: We are, or want to be, or should be dedicated to functional explanations in the sciences, or at least the special sciences. Therefore—according to the principle that what exists is what our ideal theories say exists—we are, or want to be, or should be committed to metaphysical functionalism. Let us call this the _argument from functional_ _explanation_. I will try to reveal the motivation for making such an argument, and sketch the kind of response that should be made by critics of functionalism.

Consciousness and evolution are complex phenomena. It is sometimes thought that if adaptation explanations for some varieties of consciousness, say, conscious visual perception, can be had, then we may be reassured that at least those kinds of consciousness are not epiphenomena. But what if other varieties of consciousness, for example, dreams, are not adaptations? We sort out the connections among evolution, adaptation, and epiphenomenalism in order to show that the consequences for the nature and causal efficacy of consciousness are not as dire as has sometimes been supposed.

Forthcoming in Philosophy of Science. Despite some recent advances, multiple realization remains a largely misunderstood thesis. Consider the dispute between Lawrence Shapiro and Carl Gillett over the application of Shapiro’s recipe for deciding when we have genuine cases of multiple realization. I argue that Gillett follows many philosophers in mistakenly supposing that multiple realization is absolute and transitive. Both of these are problematic. They are tempting only when we extract the question of multiple realization from the explanatory context in which it is invoked. Anchoring multiple realizability in its theoretical context provides grounds for arbitrating disagreements. Doing so, I argue, favors the view advanced by Shapiro.

A common view is that the truth of multiple realization—e.g., about psychological states—entails the truth of functionalism. This is supposed to follow because what is multiply realized is eo ipso realized. I argue that view is mistaken by demonstrating how it misrepresents arguments from multiple realization. In particular, it undermines the empirical component of the arguments, and renders the multiplicity of the realization irrelevant. I suggest an alternative reading of multiple realizability arguments, particularly in philosophy of psychology. And I explain the proper way to understand the relation between realization and multiple realization

Saul Kripke’s modal essentialist argument against materialism remains an obstacle to any prospective Identity Theorist. This paper is an attempt to make room for an Identity Theory without dismissing Kripke’s analytic tools or essentialist intuitions. I propose an explanatory model that can make room for the Identity Theory within the constraints of Kripke’s view; the model is based on ideas from Alan Sidelle’s, “Identity and Identity-like” . My model explains the apparent contingency of some scientific identities by appealing to our epistemic access to the conditions of identity for sensations and brain processes. Pace Kripke, the Identity Theorist can thus explain away the apparent contingency of mind-brain identity claims