Posing the Mind-Body Problem
Often the best (and only) way to make progress on a problem is to pose it in the right form. In that spirit I propose that we divide the classic mind-body problem into three interconnected but distinguishable problems: the problem of substance, the problem of structure, and the problem of content. Suppose we seek a characterization of a certain class of objects—material bodies, organisms, minds, what have you. We first want to know what the objects are made of—their composition or substance. We can answer that question at different levels of analysis, but in the case of organisms (say) we could cite chemical composition and cellular composition: organisms are made of chemicals and cells (we might then go on to say that these are composed of atoms, which are in turn composed of matter and energy). We could also reply that organisms are (partly) composed of vital spirit conceived as disjoint from matter, if that were our inclination. With respect to the question of structure, we can reply that organisms are divisible into separate organs that function together to aid the survival of the organism: they are not homogeneous entities but differentiated entities (unlike various inanimate objects). This is an abstract description pitched at a general level with no mention of specific organs and without reference to the question of substance: it concerns what might be called “formal architecture”, neutral with respect to specific implementation or underlying substance. The question of content is answered by listing the specific organs possessed by organisms: heart, kidneys, liver, skin, brain, etc. These are the contents of organisms—literally what they contain. In principle these organs can vary while keeping formal architecture constant, and can stay constant while varying underlying substance. By answering each of the questions we achieve what has a claim to be a complete characterization of the objects in question. Much the same can be done for inanimate objects: they can be described as being composed of matter and energy; they can be described as having a continuous structure or a granular structure, as well as having spatial and quantitative relations; and they can be described by reference to particular kinds of component, such as electrons and protons, or different chemical compounds. The types of description are compositional, architectural, and componential: what the constituting substance is, what the abstract form is, and what the actual components are (which includes their specific character and properties). We have here a tripartite format for exhaustively characterizing a class of objects, applicable across the board.
We can apply the format to minds: what is their substance, what is their form, and what is their content? Now everything becomes more controversial, though we might try to venture answers that don’t beg big questions: mind as composed of consciousness, mind as having a modular form, mind as containing belief and desire. These modest replies, however, elicit obvious objection, and anyway don’t tell us what we want to know. The kind of answer we seek can be drawn from the following list of possibilities: mind as composed of immaterial substance or material substance or dual-aspect substance or formal computations; mind as having the structure of discrete combinable symbolic units or of dispositions or of continuous quantities or of functional states; and mind as containing elements of rationality or intentionality or subjectivity. I want to emphasize the second kind of description because it tends to get overlooked: the mind has abstract structural properties that raise questions about its relation to the brain—for example, the discrete combinatorial infinity of the language faculty (how is this implemented in the brain?). Depending upon how we choose to answer the three questions, we get a different set of issues with respect to the relation between mind and brain–different explanatory problems are raised. For instance, if mind is made of immaterial substance, has a continuous structure (no mental atomism), and is characterized by subjectivity, then we obviously have major questions about its relation to the brain, since the brain is material, has discontinuous structure, and contains nothing subjective. There will be no possibility of reduction and the problem of interaction will loom large. But if the mind is composed of material stuff, has an atomic structure, and contains computations, then we have a less challenging set of questions, since the brain looks capable of matching each of these descriptions.
My aim is not to adjudicate between the various possibilities but to provide a format for posing them: the mind-body problem is really a cluster of three different sorts of problem. No doubt there is overlap, but it aids clarity to keep the three problems distinct. Descartes was particularly interested in the composition problem; recent analytical philosophy has focused on the component problem; the architecture problem has received less attention (though one can read Chomsky as exercised by it, given his characterization of the structure of the language faculty). We certainly can’t favor a reductive view of mind if we have determined that mind has a structure that the brain simply doesn’t possess (particularly in regard to thought and language). In order for a reductive view to work, the mind must be made of what the brain is made of, it must have the structure of the brain, and it must not have contents that the brain lacks. Recent discussions that focus on the nature of mental events and states (type of token) fail to take the full measure of the problem; they don’t pose the problem in the right way. The question must be whether the mind, characterized in the ways outlined, reduces to the brain, not merely whether mental events are identical to brain events.
From an expository and pedagogical point of view, I recommend this tripartite articulation of the mind-body problem (whether it brings us closer to a solution is another question). It poses the problem in all of its aspects. The question ought to be whether the general nature of the mind is explicable in terms of the general nature of the brain—and that concerns composition, structure, and content. My own view (which I won’t defend here) is that the substance of the mind is the substance of the brain, but form and content pose insuperable problems: that is, the brain has inexplicable emergent properties.