  In any case, there are other conceptually coherent scenarios that are considerably more straightforward than an inverted spectrum scenario, for example a scenario containing a conscious subject and a functional duplicate who is not conscious at all (a “zombie”, in the philosophical sense). So if the move from conceptual coherence to possibility is in fact legitimate, functionalism may be refuted by a simpler argument that does not have an inversion hypothesis as a premise. (Shoemaker is a notable dissenter on this point; he holds that while inverted spectrum scenarios are conceptually coherent, zombie scenarios are not. See Shoemaker 1975a, 1981, 1991.)