Is it Epistemically Possible that the Mind is Reducible to the Brain?

Is it Epistemically Possible that the Mind is Reducible to the Brain?

Might it turn out that the mind can be reduced to the brain? Are we now under an illusion of irreducibility that could be rectified in the future? The answer I want to give is yes and no. Let’s be specific: might it turn out that pain is reducible to C-fiber firing? I want to say (a) that it could not turn out that pain is reducible to C-fiber firing, as these things are now conceived, but (b) pain could turn out to be reducible to C-fiber firing if differently conceived. In effect, I think there is an ambiguity in reduction statements, a kind of scope ambiguity. It is true of pain and of C-fiber firing that the former could turn out to be reducible to the latter, but it is not true that pain could turn out to be reducible to C-fiber firing, where the two referring terms are taken as occurring within the scope of the “it could turn out” operator. That is, it could be true de re of pain and C-fiber firing that the former reduces to the latter, but not true de dicto that pain is reducible to C-fiber firing—not true of those things under those descriptions. Reducibility contexts are opaque not transparent; therefore, scope distinctions apply to them. Pain qua pain is not reducible to C-fiber firing qua C-fiber firing, but the things themselves might stand in the reducibility relation under other descriptions. In order to obtain a true de dicto reducibility statement, one would have to insert different descriptions; but the de re statement will be true under the non-reducing descriptions—even if those descriptions are not humanly accessible (i.e., if mysterianism is true). If we describe pain as “ABC” and C-fiber firing as “XYZ”, then we can get a true reduction statement of the form “ABC is reducible to XYZ”, but not by using “pain” and “C-fiber firing”.

Let me try to clarify matters. As things are, “water is reducible to H2O” is a true reduction statement (or we can assume so). But suppose we imagine a society rather like ours in which people have some pretty wacky beliefs: they think of what we would call chemical elements as little demons, and they believe that water is composed of such demons. They will then say that water is made of these demons—call them the “X-demon” and the “Y-demon”—conceived as invisible intelligent beings. And suppose that when they use these terms, they are actually referring to oxygen and hydrogen, though they don’t know this. It is then true of the referents of their terms that water reduces to those referents, but is it true that water reduces to an X-demon and a Y-demon, where these denoting terms are given narrow scope? Intuitively not, because this is the wrong way to think about the constituents of water—a kind of pre-scientific mythology. There is no reduction under those descriptions, but substituting other terms for them with the same reference yields a truth. We have reduction de re but not de dicto, though our terms (“oxygen” and “hydrogen”) also give a de dicto reduction. In other words, reductions have a conceptual component as well as an objectual component—like beliefs and other propositional attitudes. This is not surprising given that reduction is connected to explanation, which also produces intensional contexts. The same kind of thought experiment applies to heat and light: if the proposed reduction base is described in sufficiently outlandish terms, this will not yield a true reductive de dicto proposition. It is no use describing what is going on inside hot objects as (say) a collection of tiny nuns rowing boats, even if this description actually picks out molecules in motion (a “referential” use in the terminology of Donnellan); you can’t reduce heat to molecular motion under that description. You can’t have a true de dicto reductive belief if you wildly and absurdly misdescribe the reduction base. Similarly, for light and “storms of fairy dust” instead of “streams of photons”, even if the former refers de facto to the referent of the latter. Just so, if “C-fiber firing” is wildly inadequate as a concept–you will need to find a better description of the referent of this term. Under that description, there is no de dicto reduction, but under another description (possibly one of which you have no knowledge) there is such a reduction. It will never turn out that pain is reducible to C-fiber firing (de dicto), but it may well turn that that pain is reducible to PRQ, this being a better description of the referent of “C-fiber firing”. If future science starts talking about the brain with new concepts, it may be that it will produce adequate reductions both de re and de dicto; meanwhile all we have is a true de re reductive statement, viz. “It is true of C-fiber firing that it reduces pain (but not qua C-fiber firing)”. Currently, we think of the brain as consisting of “fibers” that “fire”, but these may be the brain demons of the future—there may be no such things in future brain science. The brain might indeed be totally inconceivable by us in its true objective nature (its “deep structure”). In any case, it is logically possible for pain to be both reducible to C-fiber firing and not reducible to C-fiber firing, once we articulate the scope ambiguity I have detected. I think it is quite likely that we now know a number of true psychophysical de re reductions, but have no de dicto knowledge of such reductions; and yet these reductions exist in conceptual space.[1]

[1] This position explains why we think both that the mind is obviously not reducible to the brain and that it most certainly is so reducible. It has to be reducible somehow, even though we don’t know how—and the way we now view the brain is clearly inadequate. It makes sense of our epistemic situation. The case is just like the question of whether someone who has never heard the name “Hesperus” believes Hesperus is Phosphorus: he does believe of Hesperus that it is Phosphorus, but he doesn’t believe that Hesperus is Phosphorus.