On Mind-Brain Relations
Various relations between mental events and brain events have been (and could be) posited: correlation, causation, simultaneity, supervenience, spatial coincidence, composition, part-whole relations, and identity. It is fair to report that these relations are first found outside of the mind-brain relation and then applied to that relation; we don’t come up with them by considering the mind-brain relation itself. That is, they stem from the physical world not from the psychophysical world: we transfer them from their original home in the physical world to the special case of mind and brain. Hence analogies are often drawn between the psychophysical case and physical cases—for instance, “pain is C-fiber firing” is like “heat is molecular motion”. This is already suspicious, since we are not deriving the relations from direct inspection of the mind-brain nexus: we are not examining that nexus and concluding that a particular relation is the right one to characterize it. Rather, we are extrapolating the relation from elsewhere and postulating that it applies, not observing that it does. Thus there is a big difference between our knowledge in the two cases: we can experimentally establish that heat is molecular motion, for example, but not that pain is C-fiber firing. Or, to take a more transparent case, we can observe that Superman is Clark Kent simply by seeing Clark Kent change into his Superman clothes and fly off; but we can’t do anything comparable with the claim that mental events are identical to brain events—we can’t witness the transformation. Instead we postulate an identity; we don’t discover it. It is the same with all other ordinary identity statements: we empirically discover that these identities hold. So it is not a mere theory that a is identical to b; it is an established fact, known by empirical means. By contrast, the identity theory of mind and brain is a speculative theory, a bold conjecture, not something we have empirically established to be true. And similarly for other theories of the relation between mind and brain, such as that mental events are composed of physical events or are spatially coincident with them. True, we can empirically establish correlations, but the step to identity or composition is always a move away from observation—a philosophical theory rather than a piece of empirical science. We apply relations drawn from elsewhere, but we don’t carry over the methods that are generally used to assert their existence. Thus the theories remain controversial (but no one seriously disputes that Hesperus is identical to Phosphorus or that water consists of H2O). The justification for asserting the theories tends to be abstract and general—isn’t it more parsimonious to assume identity, and good to avoid the absurdities of dualism? It is never stated that we have simply discovered by observation that pain is the same as C-fiber firing—by looking at it from different angles or by using a microscope or by tracing it over time. We discovered that butterflies and caterpillars are the same organism by observing the chrysalis stage; we didn’t just posit the identity on the grounds of Occam’s razor or fear of butterfly-caterpillar dualism.
It would obviously be better to arrive at a theory of the mind-brain relation by examining the case directly. After all, it may be that physically based relations of the familiar kinds do not apply in this case—maybe there is a special kind of relation that connects the mental with the neural. So shouldn’t we concentrate our attention on the specifics of the mind-brain nexus and work from there? The trouble with this is that nothing suggests itself. We don’t get even a hint of what the relation might be by introspecting our pains and observing our brains; we find only correlations not a theory of the connection between the correlated entities. Maybe they are identical, but nothing in what we observe suggests as much; they don’t even seem similar. At least we can see that Hesperus and Phosphorus are both planets, and that Superman and Clark Kent are both men, but we can’t see that pain and C-fibers are both anything (except maybe events); there is not even a hint of the possibility of identity (or composition, etc.). If the relation is that of identity, this remains hidden from us, not something that reveals itself to diligent observation. Why? Why does the mind hide its true relation to the brain, and hide it so well? If it is true that pains are composed of strands of C-fiber, then why is it that nothing in our experience suggests that? Why can’t neuroscience prove it? Physics proved that heat is molecular motion, chemistry proved that water is H2O, biology proved that the heartbeat is a pumping muscle, and astronomy proved that Hesperus is Phosphorus; but neuroscience is incapable of proving that pain is identical to C-fiber firing. Is that perhaps because it isn’t? Does it bear some other relation to the correlated brain events, some relation we don’t know about, or can’t even imagine?
It is possible that we are thinking about this all wrong. We shouldn’t be hunting for relations drawn from outside our area of interest—the mind-brain connection—and then postulating that such relations capture that connection. We should instead focus on the case at hand and try to forge a theory of the psychophysical nexus that respects its special character. Don’t think, look! The problem is that nothing comes to mind: we look, but we don’t find. The psychophysical nexus just stares blankly back at us, elusive and enigmatic. Here the pain, there the brain: but where the linkage? There must be some sort of intimate relation, since the two are not just accidentally joined, but for the life of us we can’t figure out what it is. Let me introduce some neologisms: let’s say that the brain state “mentalizes” and the pain state “physicalizes”—that is, they each do something that leads to the other. This doesn’t tell us how they do these things, only that they do. Then the question is what these peculiar relations involve: what theory of them is correct? Pain is such that it physicalizes itself as C-fiber firing, and C-fiber firing is such that it mentalizes itself as pain: now the question is how that happens. A formidable question indeed, and one formulated by using a pair of murky neologisms; and yet it at least points us in the right direction—what is it to mentalize and physicalize? We know what it is for Phosphorus to “Hesperusize”—to follow the same path through space and time as Hesperus does—but what is it for C-fibers to mentalize (specifically painize)? That is the question; and we will not seek to answer it by borrowing concepts drawn from somewhere else. We need concepts tailored specifically to the case at hand. Whether we can find or devise such concepts is another matter. Mysterians remain doubtful: we simply have no viable way to infer the relation from the relata. There might be identity for all we know, but the usual paradigms of empirically discovered identities provide no guidance in this alien territory, being mere impositions from outside. All we can claim is that the relation must be close, intimate, and transparent (not brute). It must be such that it takes the enigma out of the connection, and makes it something other than a mere conjecture, backed by nothing but Occam’s razor and dualism-phobia. It must be like the empirical discoveries that underlie ordinary assertions of identity (“I saw Clark Kent put on his Superman clothes and then fly off”). As things stand, however, we have no clue about how to do any of this, but merely struggle with concepts borrowed from areas less intractable, as in “You know what identity is from the case of Hesperus and Phosphorus; well, mind and brain is just like that”. But it is not just like that because we can’t apply the methods used to establish the former identity to establish the latter (putative) identity. What I tend to believe is that the psychophysical nexus is nothing like the standard paradigms, just in a different league or galaxy; and that it is completely misguided to employ the usual types of relations in an effort to understand it. It is not so much that the identity theory, say, is false as that it provides no illumination at all, because the standard cases of identity are so far removed from the case at hand. We need a completely new way of thinking if we are to get anywhere in grasping the true nature of the mind-brain connection; and it is a real question whether this new way is available to us. What is certain is that we will never achieve it if we lazily rely on concepts designed for a quite different purpose. It is as if we are trying to understand electromagnetic phenomena solely on the basis of traditional mechanics instead of recognizing that something completely different is afoot, calling for a new conceptual apparatus. The very idea of using concepts like identity and composition, explained by way of the standard paradigms, is hopelessly wide of the mark, signaling desperation rather than insight. We should forget all such paradigms and start afresh, always being aware that there is no guarantee of success. But failure is better than complacent illusion.
 I can put the point very simply: it is no use trying to construct a theory of the psychophysical nexus by comparing it to cases in which nothing mental is involved. This is merely the triumph of wishful thinking over honest toil.