Metaphysics (or “ontology”) is the study of what exists (Aristotle called it the study of “being”). To many people today metaphysics seems anachronistic. Haven’t we settled the issue of what exists, they might ask, in favor of the physical universe? And isn’t natural science the way we produce knowledge about this universe? How could more work in metaphysics possibly generate any persuasive arguments, if “metaphysics” is not simply “physics”? Arguments about the relationship between the mind and the body that aren’t grounded in empirical research of some sort can’t hope to be legitimate in a world awash in data from experimental psychology, neuroscience, computer science, evolutionary biology, linguistics and the myriad of interdisciplinary areas of research that today we call “cognitive studies.” Isn’t a metaphysician a mere poet of speculation? Diverting at best, but such a person has no hope of producing useful knowledge. That, anyway, is the drift of the reaction one frequently gets when proposing to discuss the metaphysics of the mind/body problem. I will respond to this initial “meta”-challenge in two ways.
First, I completely embrace the spirit, and much of the letter, of this initial objection. I too take it as axiomatic that what exists is the physical universe (by “physical” I mean the universe of matter and energy, or maybe matter/energy; I don’t pretend to be sophisticated about theoretical physics). I don’t think that humans are composed of physical bodies and non-physical souls, like a traditional mind/body dualist. I think that humans are physical through and through, animals that evolved here on earth through a long process of evolution the contingencies of which were, and continue to be, bounded by the constants of biology, chemistry, and physics. I don’t expect to discover that humans are angels, or that the physical universe is an illusion and humans are non-physical spirits, or anything like that.
To be more specific, I have a view about the metaphysics of humans that I call anti-humanism, a loaded phrase taken as rhetoric but used here only to mean this: the universe may be as magical, mysterious and mystical as it may be; I don’t know anything about the ultimate composition or nature of the universe. I have no interest in making a brief for reduction, as if natural science has already revealed the nature of being, or even potentially could. I don’t even know what we’re talking about when we use that kind of language. My claim is much humbler: whatever nature in general is like, humans are like that. Humans are not miracles, if a “miracle” is defined as an exception to the laws of nature. I hold the anti-humanist view simply because I know of no reason to think that humans are miracles; I stress it because a deeply internalized assumption of human exceptionalism continues to be a barrier to progress across the whole area of cognitive science.
Which brings me to the second response to the objection that metaphysics is anachronistic: it is certainly not true that the contemporary community of educated people embrace anti-humanism as I just defined it. For one thing, a great many college students, most people walking down the street and the overwhelming majority of the world’s population today continue to think that the mind (taken, that is, in the metaphysical sense of some thing that exists) is something distinct from the body or, at least, that mental phenomena cannot be adequately described and explained in wholly physical terms. This conviction has many variants that range from traditional, usually religion-based beliefs about souls, afterlives and so forth to more modern notions, such as the view that a naturalistic view of human nature is perniciously reductive and to be resisted by the liberal-minded, or perhaps that science itself is nothing but a socially-constructed “conceptual scheme” with no particular claim to legitimacy, and so on. For another thing, very sophisticated versions of human exceptionalism exist in the academy (for example among some linguists), such that it is by no means established conventional wisdom that physical science subsumes psychology by metaphysical axiom.
That’s why the topic continues to be exciting. We live in a world where most natural phenomena, from the micro level of atoms, cells and molecules up to the macro level of galaxies and the universe itself, seem to be describable and explicable in physical terms. Physicalism (I mean by this term the metaphysical position that only the physical universe exists) is not totally triumphant (and it is a reasonable point that contemporary physics itself presents us with a still-mysterious and newly-strange picture of the universe). There are ongoing popular metaphysical arguments about evolutionary biology and about cosmology, for example. But it is a striking fact about contemporary culture that psychology (and by extension the behavioral and social disciplines) are still not considered to be integrated into our otherwise generally physicalist metaphysics. Put another way, while many people today have firmly internalized physicalist intuitions about organic life, say, or about distant celestial objects, physicalist theories of mind still meet with resistance even among secular, science-educated people.
A note on terminology: Consider three words, “materialism,” “physicalism,” and “naturalism.” There is a worthwhile philosophical discussion to be had about the relationships and differences between these three concepts. “Materialism” might be the view that matter (matter/energy) is the only thing that exists, “physicalism” the view that the physical universe is the only thing that exists, and “naturalism” the view that only nature exists. Obviously there is a lot of fleshing out to do to make those terms very coherent. I’m not going to work on that here. Connotatively “materialism” sounds the most reductive, “naturalism” the most open-minded, so people inclined to inject ideological considerations will linger on these distinctions, no doubt a potentially useful thing to do but not something that particularly interests me in the present context. I am going to paint with a broader brush and assume that my charitable readers will get the larger drift: these words all point towards a broadly naturalistic monism, versus metaphysical heterogeneity or dualism. I will mostly, but not exclusively, use the term “physicalism” and stick with my definition that this is the view that only the physical universe exists.
Metaphysics is not something that is replaced by physics. Physicalism is a particular metaphysical position. Everyone has metaphysical assumptions, articulated or not, whether they want to or not, and they always will. The person who chafes at the idea that there is still a need for explicitly metaphysical discussion is claiming that our shared metaphysical assumptions are currently stable, not that “there is no such thing as metaphysics,” although they may unreflectively put it that way. I agree that physicalism is currently the ruling metaphysical paradigm, at least among cognitive scientists, psychologists, philosophers and so on, and I too labor within this paradigm, albeit with some important qualifications that are discussed in the second part of Chapter Two.
It’s not enough, however, to just assert one’s acceptance of a broadly physicalist, or naturalist, metaphysical attitude. Our work here is not done. For dualists, including many philosophers working in the classical, medieval and early modern periods of European philosophy through to 19th century transcendental idealism, the “mind/body problem” was the problem of explaining the interaction of the physical with something non-physical. Plato and Descartes are examples of excellent philosophers who saw the problem this way. For the physicalist the problem is different (and, yes, there are third ways, such as Spinoza’s “double aspect” approach, that are important and useful and that will be discussed where appropriate). The physicalist wants to naturalize psychology: to integrate psychology into the broader naturalistic worldview. And that we have yet to do. To see this, I’ll conclude this preliminary discussion of metaphysics in general and get to the specific problems of philosophy of mind.
If “metaphysics” still sounds too far out, consider the relationship between metaphysics and semantics. Say someone is talking about angels. The word “angel” is the subject-noun in their sentences. In good faith (pardon the pun), we would like to understand what they are saying to us. “What are you referring to,” we might ask, “by this word ‘angel’?” If, as one might suspect, it turns out that our friend means to be referring to non-physical entities, some people will demure because they doubt the existence of non-physical entities per se. This is the source of the old cliché of the philosopher as someone who insists that we “define our terms”: philosophers are sensitive to the metaphysical assumptions revealed by language (and of course we’re all philosophers, just as we’re all musicians; these are basic questions that everyone asks, just as everyone enjoys a good tune). In that sense, metaphysics and semantics come to the same thing.
It’s not just entities but also properties that are part of existence, or of what we refer to as existing. In philosophy of religion (a useful example just because most people have thought about it) we find references to metaphysically interesting entities: God, angels, heaven and so on. In other areas, such as aesthetics and ethics, we find references to all sorts of metaphysically interesting properties: beauty, goodness, justice etc. Just as we might be skeptical of the existence of non-physical entities, so we might be skeptical of the existence of non-physical properties. That is, a physicalist might hold that all properties are physical properties (that is, that only physical properties exist) just as they hold that only physical entities exist. In fact we can just define “philosophy” as metaphysics and epistemology. Any discourse that makes metaphysically and epistemologically unusual references comes under the purview of the philosopher. These topics include (but are not limited to) aesthetics, ethics, logic, mathematics, politics and society, religion, the nature of science itself…and psychology.
Another introductory note on terminology: By “psychology” I don’t mean the academic discipline that goes by that name and in which specialists receive formal degrees. I mean the ordinary, everyday discourse, practiced by everyone, that we traditionally use to explain behavior. “Why did he leave the room?” “He wanted a drink of water.” “Does she like chocolate?” “Yes she does.” “Are you in pain?” “I’m OK.” I mean nothing more nor less by “psychology” than that kind of talk, and the assumptions and conceptualizations that underlie it. That is where we find the metaphysically interesting language.
Psychological language makes frequent reference to all sorts of mental entities and properties. In religious talk (to stick with the most obvious analogy) we find words like “God,” “angels,” “faith,” “prayer” and so on. When I say these are metaphysically interesting words I mean that they don’t seem to function in the way that grammatically similar words from more quotidian discourse do. I can understand “The table is in the room” without any metaphysical trouble. I cannot do the same with “God is everywhere.” English speakers typically have no trouble understanding the use of the existential verb “to be” in sentences about tables, but they do in sentences about angels. For an epistemological example, one does not have faith in one’s religion in the same way that one has faith in politicians (or vice versa!). The verb “to know” is being used in an unusual way. Philosophical enquiry is needed.
Similarly in psychology we refer to, among other things, “beliefs,” “desires,” “hopes” and “fears,” also to “pains,” “sensations,” “textures” and “tastes.” (In what follows I will identify and distinguish two fundamental kinds of psychological words. That will be some of the major business of the book, so for now I will just stick to this preliminary discussion of metaphysics and method.) It’s clear enough that these are metaphysically interesting words. I don’t “have” beliefs and desires the same way that I have nickels and dimes. I don’t even have any fixable number of beliefs and desires, whereas the current number of nickels and dimes in my possession is all too definite. Sometimes I can see that my friend has a bag in his hand and sometimes I can see that my friend has a pain in his hand, and seeing it (with my own eyes) is (outside of a philosophy class!) all I normally need in order to know it, but so different is seeing his pain from seeing his bag that many people are willing to say (but usually only inside of a philosophy class) that I don’t actually know about his pain at all.
To naturalize psychology would be to give an account of the meaning of psychological words such that they were no longer metaphysically interesting. Another way to put this is that a physicalist theory of mind is identical to physicalist semantics of psychological words. The whole enterprise is revealed to be much less outlandish than it initially appears once one sees that we are talking as much about the word “mind” as we are talking about minds, as much about the word “belief” as we are talking about beliefs, as much about the word “sensation” as we are talking about sensations, and so on. Nor do I have any aspiration, as some contemporary philosophers of mind do, to change the way we talk (in fact I will explain my reasons for some doubts that we could even in principle do this).
It’s not normative psychological language that has problems. Normative psychological language is chugging along out there in the real world just fine. It’s contemporary philosophy of mind that has problems. As a philosopher of mind myself I experience this personally: there are currently two types of theories of mind, in response to two problems, and I find the arguments that motivate the respective problems persuasive, and I find the respective theories that are offered in response to the two problems to be intuitively more or less satisfying. It’s just that they are apparently mutually contradictory. It is that experience of internal contradiction in my own thinking about the subject that has motivated the present book. Without it I wouldn’t, couldn’t have developed a contribution even possibly original enough to justify writing yet another book on the philosophy of mind after several decades when we have been awash in them, many of them written by some of our best living philosophers.