 One line of argument (Block and Stalnaker 1999; Yablo 2000) contends that the conceivability of (alleged) counterexamples to psycho-physical or psycho-functional identity statements, such as zombies, has analogues in other cases of successful inter-theoretical reduction, in which the lack of conceptual analyses of the terms to be reduced makes it conceivable, though not possible, that the identities are false. However, the argument continues, if these cases routinely occur in what are generally regarded as successful reductions in the sciences, then it's reasonable to conclude that the conceivability of a situation does not entail its possibility.