Here's a quick little argument I recently cooked up against the view that possessing, at time t, concept of a red quale requires having, at time t, a red quale.
Knowing what to imagine. One relatively natural way of interpreting the suggestion that there are concepts of a quale that are possessed only when enjoying that quale is that the suggestion is equating concept possession with imagination. So, for example, in possessing the concept of a red quale, one is imagining having an experience of red. Further, this imaginative episode itself has a red quale. Such an account might be extended to the following kind of account of linguistic understanding. When one reads or hears the sentence “Smith saw a ripe tomato and thus had a red quale” one’s comprehension of such a sentence is constituted by entering into an imaginative state that itself has a red quale. Such an account may have an initial air of plausibility. Indeed when I discuss such topics with my students, it seems to be a relatively common view among them that comprehension involves the entertaining of mental images. However, such an account faces a problem that threatens to undermine the whole project of assimilating concept possession to the imaginative re-creation of the thing conceived. We can begin to understand the problem by considering the question: how does one know which quale to imagine? Consider how the question arises in contemplation of the imaginative account of linguistic comprehension. Suppose that at time t1 Jones does not have a red quale (though he may very well have had a red quale at times prior to t1). Suppose that at time t2, Jones hears (or more specifically, the relevant sounds are transduced by his auditory receptors) the sentence “Smith saw a ripe tomato and thus had a red quale.” Suppose that at time t3 Jones goes into an imaginative state wherein he imagines seeing red and thereby has a mental state with a red quale. Let us ask our question again, this time with respect to the scenario concerning Jones. How does Jones know which quale to entertain? Quite plausibly, it is at some time after t2 that he knows which quale is the correct one to imagine. Further, and also quite plausibly, it is at time before time t3 that Jones knows which quale is the right one to imagine at t3. Compare, if I am being tested on whether I know which cup a ball is under and I am to indicate my knowledge by pointing at the correct cup, then if I do indeed know, my knowledge is something I have before I point at the cup. My knowledge is one of the causal antecedents of my pointing and causes predate their effects. Similarly, Jones’s knowledge of which quale to imagine predates the imaginative episode. Now, this line of thinking spells trouble for the suggestion that the concept is identical to the imaginative episode, since it is far more plausible to identify the concept with the state of knowledge that predates the imaginative episode.