Brains in vats and semantic externalism: a new response to the skeptical argument

Abstract It has been argued that since we cannot rule out that we are eternal brains in vats ( BIV s) whose sensory impressions are generated by a supercomputer and who can thus be assumed to exist in a world where (almost) nothing is as it seems, most (or almost all) of our empirical beliefs are such that we cannot rule out that they are false. Since fallible knowledge seems to be a contradiction in terms, it has been concluded that we have much less empirical knowledge than we would normally assume and that sound empirical knowledge might even be impossible. This is the skeptical argument. Starting from semantic externalism, various arguments have been proposed to rule out the possibility that we are BIV s. In this paper, I will argue that trying to rule out the possibility of being a BIV is a very weak response to the skeptical argument, as it accepts the challenge raised by the skeptic, i.e. that in order to have empirical knowledge, we have to exclude the possibility that we are BIV s. In fact, we will see that starting from semantic externalism, a much stronger response is possible. Accordingly, we do not have to rule out that we are BIV s in order for the skeptical argument to contain a false premise.