The identity theory of consciousness rather simply states that any given mental state is identical to some physical (brain) state. There is a weak and a strong version of this hypothesis (token and type identity respectively) but let’s not worry about that; for now let’s ask only the following questions:
A)What is meant by ‘identical’?
- What sort of question is this?
Ok, first to question A. There are typically said to be two forms of identity. The first is the run of the mill logical identity such as “x=x” or “all bachelors are unmarried men.” In these, the identity relationship is contained within the concepts themselves. For instance we know that bachelors are unmarried men simply by looking at the definition of the word ‘bachelor’. It can also be said that these sorts of relationships are necessary ones; we can not imagine a possible world in which they are not the case (ignoring the possibility that the linguistic sign representing the concepts may be different). This would seem to be unlike what we mean when we say a mental state is a given brain state. Normally, we would say that this is a contingent identity relationship; this relationship is contingent on the facts of the actual world. So, using possible worlds talk again, there could be other possible worlds in which brain states are not the same as mental states but in this one they are.
The above paragraph may mean little to many who are proponents of a sort of identity theory of the mental. These folks would simply say something like “I don’t care what sort of logical evidence you do or don’t have for saying that the mind is identical the brain; we only need to look at the one to one relationship between the specific firing of neurons and the occurrence o f mental states to prove the identity relationship.” I could dispel this reasoning by saying that although there may be a causal relationship between mind and brain this does not say anything about an identity relationship. This, of course, is the sneaky little trick up the dualist’s sleeve; one that he pulls out when he feels like others are snickering at his beliefs. One could say a similar thing about most scientific theories; for example, when we see lightening there is also a measurable electrical activity. Using the dualist’s logic we could say that a physicalist about lightening can’t prove a thing; it doesn’t have to be the case that lightening is the electrical activity, perhaps there is merely a causal relationship (or maybe just correlational) between there being lightening and there being electrical activity. Saying that lightening can not be reduced to electricity is clearly absurd and therefore saying such a thing about the mind might also be absurd.
This leads me to question B. Typically when we discuss the identity theory we think that we are talking about something very general. Meaning, if we can decide this problem now the answer we come up with (if it is correct of course) will be valid forever. So, when we try to formulate an answer it shouldn’t just be the best we have right now; we should have good reason to think that it is actually true. In science we can often get away with horrible models, if they work better than the alternative (in some cases no model at all). However, in philosophy the opposite is true; if a model isn’t satisfying, if it can’t explain major aspects of a phenomenon we would rather just call such a phenomenon a ‘mystery’ (at least for the moment). I think that this is the best way to attack current versions of brain based identity theories. They simply address the wrong question. It is true that they are far more useful (in a scientific sense) than any sort of dualism (which is largely useless) but it seems to me that they share dualism’s inability to explain a large number of mental phenomena. The existence of subjective experiences is one of these unexplained phenomena; there is no model in existence which can truly explain the fact that we have subjective experiences. Of course neuroscience can explain the content of these subjective experiences (such as how afterimages are formed and how ideas are formed) but the simple existence of subjectivity is never really addressed by proponents of an identity theory.
None of this is all that persuasive. For the most part, physicalists will go on asserting that dualism is absurd and dualists will keep on pointing to the subjective nature of mental states as ‘perfect’ proof that physicalism must be false. I would rather take a middle ground. In one sense I do consider myself to be a physicalist; in most of my thinking I make the implicit assumption that the mind and brain are one thing, in a very general sense. It seems implausible (and not all that helpful) that there would be a separate realm of existence in which all those subjective states existed. Since dualism doesn’t offer any real enlightenment (it pretty much just says that mental things exist apart from the physical without any explanation of how this other reality functions) it seems an unneeded liability. I would rather take a less radical position; our subjective mental states probably exist in physical reality but our current idea of how the brain works is in need of a paradigm shift before we can ever hope to explain subjectivity in physicalist terms. You can’t explain consciousness with neural networks of any sort; sure, you can explain how a system could be self monitoring, or how a brain can work as a cohesive system, but the fact that all these become subjectively aware processes is a flat out mystery.
So, give me an enlightening explanation how subjectivity works or stop being boastful about how much we know about the mind.