Functionalism is the claim that mental states are individuated by what they do and not by how they are instantiated, or what their `substrate’ is. Shoemaker is responding to an objection from Block and Fodor to the effect that functionalism cannot accommodate qualia, viz.: what it is like to be in a particular mental state. There are links here to Chalmers’ `hard question’: why is it like that, or indeed, why is it like anything at all to be in a particular mental state. The motivation for the objection is that some mental states may be individuated by what it is like to be in them.
The objection proceeds by considering the possibilities of inverted qualia and absent qualia. The first means that it may be different for me when I am in the same mental state as you. The second means that it may be different for me in that there is nothing it is like for me to in the same mental state as you even though that state does indeed have phenomenological character for you. Both possibilities would be fatal for functionalism, since there would be finer grained distinctions between my mental state and yours which moreover, are differentiated by phenomenological characteristics and not functional ones.
Shoemaker asks whether it is plausible to suggest that the phenomenological character of mental states could be unrelated to their functional role in terms of what inputs, outputs and connections to other mental states it has. Presumably a mental state associated with the phenomenological character of `intense pain’ is connected to a strong desire to move into a mental state without that phenomenological character. That desire would be lessened if the `intense pain’ state had no phenomenological character, or could be eliminated entirely if what I feel as pain is what you feel as pleasure. This seems to comport poorly with the idea that we are in the same mental state at all, if that question is decided on functionalist grounds.
Q: Do qualia exist?
Shoemaker allows for the possibility of inverted qualia by describing a possible case where we could detect that someone’s qualia had shifted. The argument depends on the idea that we sometimes have difficulty distinguishing closely related pairs of shades where they are, perhaps, on the blue/green boundary. If someone’s phenomenological experience on seeing blue became exchanged with what previously they had experienced when seeing orange, then they would now find it easier to distinguish shades on what is still, in the world and for the rest of us, on the hard to pick out blue/green boundary. If this thought experiment is coherent, it eliminates the Wittgenstein problem that qualia inversion would be undetetectable from behaviour and thus a meaningless claim. Thus Shoemaker gives the objection its maximum force by admitting that inverted qualia are possible.
Shoemaker’s defence of functionalism is suggested by the problematic disconnect discussed above between phenomenological character of mental states and their function. He admits that for the defence to be successful, phenomenological characters must be integrated with the functional framework i.e. phenomenology must have a function.
Finally, Shoemaker’s argument devolves to the following. There can be a qualitative belief that one is in a state having some propositional content, which content quantifies over qualitative states but does not refer to particular qualitative states. Such qualitative beliefs are functionally definable.