Putnam on brains in a vat

Abstract

In his recent book, entitled Reason, Truth, and History, (Cambridge University Press, 1981) Professor Putnam has announced a startling discovery. I am claiming he says that there is an argument we can give that shows that we are not brains in a vat (p. 8). The supposition that we are actually brains in a vat, although it violates no physical law, and is perfectly consistent with everything we have experienced, cannot possibly be true. It cannot possibly be true because it is, in a certain way, self-refuting (p. 7). This brains-in-a-vat thesis is startling because if it is right, it refutes the widespread belief that epistemological scepticism, however intuitively implausible, is an internally consistent philosophical position. Putnam's argument is an application of what is known as the causal theory of reference. According to this theory, the meaning of a term is not determined by anything that goes on in the minds of the speakers (or thinkers) when they employ the term. Rather, it depends on 'the actual nature of certain 'paradigms" and on 'one's direct or indirect causal relations to those paradigms' (p. 42). A term such as 'tree', for example, refers to whatever objects happen to initiate the causal chains eventuating in our tree-experiences; it is quite possible that we entertain completely erroneous ideas as to what sort of objects those are. Although I do not subscribe to this theory of reference, it is not my intention to question it in this paper. My aim is to examine Putnam's argument to see whether it validly derives the brains-in-a-vat thesis from the theory. What I want to show is that Putnam's argument is a non-sequitur and that the causal theory of reference is powerless to rule out the possibility that we are brains in a vat. The task of showing this is unfortunately somewhat