We do not at present possess the conceptual equipment to understand how subjective and physical features could both be essential aspects of a single entity or process.
Suppose, as seems likely, that I taste the smoke of my cigar when and only when my brain is in a certain physical state. What gets in the way of the thought that the experiential state of which I am introspectively aware is the physical state? The problem lies in the lack of any conceivable internal connection between a modification of my subjective point of view and a modification of the physico-chemical activity of my brain. The two may correspond extensionally as exactly as you like, but identity requires more than that. If they are the same state, it must be impossible for the one to exist without the other. And while we may have good empirical reasons to believe that that is true, the understanding of such an impossibility requires
that the necessity of the connection between the two become intellectually transparent to us. In the case of conscious states and physiological states, it isn't just that we don't see such a necessary connection: it seems in advance that a necessary connection between two such different things is unimaginable. They seem logically unrelated. It is very different from trying to imagine the possibility of a physico-chemical analysis of embryonic development, before one has the slightest inkling of what the analysis might be. In that case we can nevertheless understand the possibility in the abstract: there are no grounds for ruling it out a priori, since we know in general terms what it is to exhaustively analyze a large scale process into its microscopic or submicroscopic components. But that model will not help
us with the mind and the brain. We are entitled to identify a familiar physical phenomenon like fire with a theoretically described process at the atomic level because the macroscopic properties of fire, including its causes and effects, can be derived from the microscopic account -- can be
seen to be necessitated by it. The chemical analysis of fire and air reveals, for example, that it is a necessary truth that a fire confined to a small, airtight space will quickly go out. But we cannot see how a detailed account of what is going on in the brain could exhaustively explain the taste
of a cigar -- not even if we could see how it explained all the physical effects of such an experience. So long as this explanatory gap remains, the identification of the states remains problematic.
This does seem to call for some revision in our way of conceiving of mind, or matter, or both. The difficulty is to do this without denying what is in front of your nose. What we need is not a reductionist or eliminative revision but an expansionist one. By this I mean a conception that will permit subjective points of view to have an objective physical character in themselves.
The reason such an expansion does not seem to me out of the question is that it doesn't involve a contradiction with the essential nature of subjective experience. Our problem is that there is no room for a necessary connection with physiology in the space of possible development defined by the concept of mind. But that does not rule out the possibility of a successor concept of mind which will both preserve the essential features of the original and be open to the discovery of such connections. This kind of thing happens all the time in the course of scientific history, as with the concepts of sound, or element, or species, or space, or number. A new concept is developed to talk about the same things as the old, one that includes most of the features of the old concept but puts them in a relation to one another and to other features that is new, and that makes it possible to see or explore further connections.
Without such an expanded conception of the mental there is no prospect of overcoming the explanatory gap.
