How Many Mind-Body Problems?
We tend to speak in the singular about the mind-body problem: the mind-body problem. But is that realistic? Couldn’t there be many mind-body problems depending on what aspect of the mind we are considering? They may not present the same problem or have the same solution. How many life-matter problems are there? That depends on how many kinds of life there are: carbon-based, silicon-based, light-based, etc. In each case different explanations apply. Life on earth is just one possible way to construct living things. Is there just one function-materials problem? Functions can be performed in many ways, by different types of material—metal, glass, plastic, wood, etc. Each does it differently. The mind has several components or faculties—sensation, perception, emotion, thought, language—each with its own distinctive nature. Maybe the mind-body problem is different for each part of the mind. After all, these mental capacities evolved at different times, satisfying different needs, and the mechanisms that brought them into being might be quite different. What we call “consciousness” might itself be different in each case. Some problems may be easier than others, some soluble and some not (mind-body problems and mind-body mysteries). Perhaps we would do better to think of a plurality of problems not a single problem. This is what I shall argue.
The mind falls into a number of natural kinds. It is not clear what unifies them. Some have thought it is mere family resemblance. If you think that way about games, there is no single game-action problem, but a family of different problems: what actions make chess a game, what actions make baseball a game, etc. Likewise, there is a sensation-body problem, a perception-body problem, an emotion-body problem, a thought-body problem, a language-body problem. We need an analysis of the mental phenomenon in question and then look to see what about the body might explain it; and we might get different answers. For example, bodily sensations are characterized by their distinctive feel—their subjective quality, what-it’s-likeness; but thoughts are characterized by their propositional content—what they are about, their intentionality. How does the body (brain) produce subjective feeling and how does it produce propositional intentionality? Surely the brain does not do these different things in the same way: it employs different mechanisms or structures or procedures. The mind also contains a conscious part and an unconscious part, but these are very different, so we should expect different explanations. The unconscious mind might be easier to explain than the conscious mind (and there are different kinds of unconscious mind). Consciousness itself divides into phenomenal feel and self-awareness—these might have different cerebral explanations. Higher-order thought theories might suffice for self-awareness while subjective sensations call for something different (panpsychism?). We can tackle each subproblem separately.
I am going to suggest, boldly, that there are precisely four mind-body problems, concerning sensation, perception, thought, and meaning.[1] There is also a fifth mind-body non-problem, which concerns what we can call character traits, though the label is misleading. Suppose we are interested in aggressiveness in ants: how does the ant brain produce this trait? We investigate the brain and discover a particular chemical that is present in all and only aggressive ants. That would solve the problem of explaining aggressiveness in ants. It is a materialist solution: the trait is reducible to the chemical (compare certain types of illness). We might find this chemical to be present in other animal species if and only if they are aggressive; it would then be the solution to the mind-body problem of animal aggression. The point generalizes to other character traits—docility, sociality, sexual preference, intelligence, introversion and extraversion, etc. These dispositions all reduce to chemical properties of the brain. In principle, this seems eminently plausible, just a matter of routine science—not any kind of deep mystery. It’s just like water and H2O, heat and molecular motion. The trait is identical to its neural basis. The same may be said of memory traces: they are the same as patterns of neural connectivity (we are not speaking of mental acts of remembering but of the “engram” itself). No one ever went Cartesian dualist on behalf of aggressiveness in ants or memory traces in the vole: these are a matter of brain physiology. Fine, no problem. But things are very different when we move to sensations of pain and the like (character traits are not sensations, not feelings): here we have an eruption of subjectivity, something-it’s-likeness. Now we have a conceptual problem, well explored in the literature (bats etc.). Pain presents a real mind-body problem (indeed, a mystery)—simple materialism isn’t going to cut it. Perception then poses an additional problem: not only does it involve sensation; it also involves reference (attribution) to the external world. It involves a primitive kind of semantics (intentionality, representation). Solving this problem will require extra machinery over and above that required to solve the sensation problem. What this machinery involves is an open question and not an easy one (it’s a “pretty hard” problem). The brain had to come up with something special in order to get perception off the ground. Thought poses a further problem—the proposition problem. Not just reference but logically connected propositional content. We don’t know what propositions are, still less how brains manufacture them (or reach out to them in Frege-Plato space). The brain will need to perform some fancy footwork if it is going to bring propositional thought into the world. Even if sensation and perception are taken care of, we have a fresh challenge stemming from thought (think of it as having a grade-three level of difficulty, like a gymnastic move). Thought took a while to take hold of the animal mind long after sensation and perception had been around for many millions of years. Then, fourthly, we have meaning—language, symbolism. This has its own puzzles, again amply discussed; we don’t even know that it exists, according to some, let alone what constitutes it. Yet the brain has contrived to manufacture meaning—a kind of high tech gimmick (like a computer chip). Meaning, they say, is massive, world-changing, earth-shattering, epoch-making. It poses yet another mind-body problem, transcending those that have come before. Which is harder, language or pain? Take your pick; both are gut-wrenchingly difficult. Each of these four problems introduces a new phenomenon to the party; each poses a separate mind-body problem. Don’t say they are all instances of the consciousness problem and hence unified into a single problem. First, that problem is by no means homogeneous, unless by stipulating a limited class of cases (as it might be, sensations). But second, the problems I have enumerated are quite heterogeneous, involving subjective feeling, perceptual reference, propositional cognition, and linguistic meaning. We can’t assimilate these, like varieties of cheese. These aspects of what we lump together as “mind” are as different as limbs, blood, skin, and internal organs. They are distinct natural psychological kinds. The solution to one of them will not automatically produce a solution to the others. The mind is a plurality, so the mind-body problem is a plurality. Compare knowledge: we shouldn’t speak of “the knowledge-reality problem”, as if knowledge is all of one kind with a uniform relation to reality. Knowledge has several varieties and hence several relations to reality (as in mathematical and empirical knowledge). I am tempted to suggest abandoning the phrase “the mind” in serious scientific writing, replacing it with talk of “minds”—as in “the minds-body problems”. We have several minds, in effect, and each poses its own problem. There has never been a good terminology for this aspect of nature precisely because it lacks internal unity; but we shouldn’t let our existing terminology blind us to the variety of what it gestures at.[2]
[1] Emotion can probably be dealt with by combining elements drawn from the Big Four.
[2] We can compare the mind-body problem with what might be called the self-consciousness-consciousness problem: how is self-consciousness related to consciousness? Are they identical or distinct? Do we need three levels of reality–body, mind, and awareness of mind? We should be open to the possibility that self-consciousness is itself non-uniform: consciousness of bodily sensations, say, might not be the same as consciousness of thoughts. So-called introspection might be a congeries of different sub-faculties, each evolved at different times, with a different basis in the brain. We group them casually together but they might be significantly different. Consciousness of self certainly seems different from consciousness of bodily pain.
