 And the key premise offered in support of this contention, going back to Putnam’s work (presented in  §1  above) is multiple realizability. This contention sets the agenda for the book: Polger and Shapiro will argue that there is not the sort of widespread multiple realization of mental states and processes that would be needed to support functionalism or realization physicalism over identity theory. Importantly, Polger and Shapiro do not deny that cases of multiple realization exist. Rather, they insist that the debate between functionalists and mind-brain identity theorists should be guided primarily by the question, 