Alex Byrne

Cohen begins by defining ‘Color Physicalism’ so that the position is incompatible with Color Relationalism (unlike Byrne and Hilbert 2003, 7, and note 18). Physicalism, in any event, is something of a distraction, since Cohen’s argument from perceptual variation is directed against any view on which minor color misperception is common (Byrne and Hilbert 2004). A typical color primitivist, for example, is equally vulnerable to the argument. Suppose that normal human observers S1 and S2 are viewing a chip C, as in Cohen’s example. C looks unique green to S1, and bluish green to S2. The problem, as Cohen has it, is to explain “what could (metaphysically) make it the case” that S1, say, and not S2, is perceiving C correctly. He purports to find the explanation “extremely hard to imagine”, and so concludes that both S1 and S2 are perceiving C correctly. (That is not the only option, of course: Hardin concludes that neither is perceiving the chip correctly.).

G&S describe the radical neuron doctrine in a number of slightly different ways, and we think this hides an important distinction. On the one hand, the radical neuron doctrine is supposed to have the consequence "that a successful theory of the mind will make no reference to anything like the concepts of linguistics or the psychological sciences as we currently understand them", and so Chomskyan linguistics "is doomed from the beginning" (sect. 2.2.2, paras. 2,3).[1] (Note that `a successful theory' must be read as `any successful theory', else the inference will fail.) On the other hand, the radical neuron doctrine is said to be the claim "that emergent psychological properties can be explained by low-level neurobiological properties" (sect. 2.3, para. 3). It is clear from the context that this can be more faithfully rendered as: psychological phenomena can be explained in (solely) neurobiological terms. But this formulation of the doctrine does not have the consequence just mentioned