The Modal Gap
Consider Kripke's gloss of the modal argument:
Let 'A' name a particular pain sensation, and let 'B' name the corresponding brain state, or the brain state some identity theorist wishes to identify with A. Prima facie, it would seem that it is at least logically possible that B should have existed (Jones's brain could have been in exactly that state at the time in question) without Jones feeling any pain at all, and thus without the presence of A. Once again, the identity theorist cannot admit the possibility cheerfully and proceed from there; consistency, and the principle of the necessity of identities using rigid designators, disallows any such course. If A and B were identical, the identity would have to be necessary. The difficulty can hardly be evaded by arguing that although B could not exist without A, being a pain is merely a contingent property of A, and that therefore the presence of B without pain does not imply the presence of B without A. Can any case of essence be more obvious than the fact that being a pain is a necessary property of each pain?
In a long essay, set out and explain the argument he gives for the untutored--that is, explain it for someone not in the class, someone who, for example, has never heard of phenomenal consciousness or the necessity of true identities. Your point in this is neither to criticize nor defend the modal argument. Rather, simply explain it in as paintstaking a fashion as a long essay (one page!) permits. (50pts)