We had just stopped with Chomsky arguing that a scientific study of human behaviour must necessarily take an internalist stance - that we must confine ourselves to studying the individual in isolation, if we want to be able to predict/account for how people act. Although it would seem that appeal to others would be quite useful in this regard (I flinched because you threw a ball at my face), this is only apparent - what actually enters into an explanation of my actions is my cognitive state, and the input I get from my sense organs.
Chomsky now addresses the second claim he attributes to Putnam: ‘studying the brain is not going to be helpful in understanding what people do.’ I think it is best to ignore what Putnam actually said, and to focus instead on the positive claims being made by Chomsky: “here’s how studying the brain might be helpful in understanding what people do.”
Take Putnam’s case: the discovery that thinking of cats evokes C.
Chomsky begins by describing an argument that he takes Hilary Putnam to have made:
In his John Locke lectures, Hilary Putnam argues “that certain human abilities – language speaking is the paradigm example – may not be theoretically explicable in isolation,” apart from a full model of “human functional organization,” which “may well be unintelligible to humans when stated in any detail.” The problem is that “we are not, realistically, going to get a detailed explanatory model for the natural kind ‘human being’,” not because of “mere complexity” but because “we are partially opaque to ourselves, in the sense of not having the ability to understand one another as we understand hydrogen atoms.