Brains in a Vat, Subjectivity and the Causal Theory of Reference
Putnam argued in the first chapter of Reason, Truth and History that it is not epistemically possible that we are brains in a vat (of a certain sort). If his argument is correct, and can be extended in certain ways, then it seems that we can lay to rest the traditional skeptical worry that most of our beliefs about the external world are false. Putnam's argument that we know that we are not brains in a vat has two parts. The first is an argument for a theory of reference according to which we cannot refer to an object or a type of object unless we have had a certain sort of causal interaction with it. The second part argues from this theory to the conclusion that we can know that we are not brains in a vat. In this paper I argue that Putnam's attempt to show that we cannot be brains in a vat is unsuccessful. However, the flaw does not lie in the argument from the theory of reference to the conclusion that we are not brains in a vat, as has often been alleged. Despite a confusion in the argument Putnam actually presents, if Putnam's theory of reference is correct, then he is also right that we cannot be brains in a vat (of a certain sort). The mistake is in the argument for the theory of reference. It rests ultimately on a false picture of the mind. First, I present Putnam's argument for his theory of reference, and the argument from that theory of reference to the conclusion that we cannot be brains in a vat. Next I explain and rebut the charge that Putnam's argument fails because if his theory were correct, we couldn't know the meanings of our words. Then I explain and set straight a confusion that creeps into Putnam's exposition of his argument. Next, I show that Putnam is after all open to the charge that his account, in conjunction with certain assumptions he makes, shows that we cannot know what we mean or think, and that what must be done to repair this undermines his argument for his theory of reference. Finally, I consider the sources of the mistake in the argument.