Brains in Vats and Semantic Externalism: New Hope for the Skeptic

Sa？etak Different thought experiments have been offered to argue for the skeptical claim that sound empirical knowledge is impossible. One of these thought experiments assumes that we are eternal brains in a vat with systematically delusory experiences. In (Putnam 1981), Putnam responds to the skeptical challenge that contrary to our initial assumption we can know a priori, i.e. independent from experience, that we aren’t eternal brains in a vat. Putnam argues that the skeptical hypothesis that we are eternal brains in a vat is inconsistent with the received view regarding reference and truth, semantic externalism, which says that a referential expression e refers to an object o if and only if e is appropriately causally related to o. There are different versions of Putnam’s argument. In this paper, I will discuss the three main versions of the argument; i.e. a reconstruction of Putnam’s original argument in (Putnam 1981), Brueckner’s simple argument (Brueckner 2003; 2016, Section 3 and 4), and a reconstruction of Brueckner’s disjunctive argument (Brueckner 2016, Section 4). It is generally assumed that Putnam’s original argument does not show that the skeptical hypothesis that we are eternal brains in a vat is inconsistent with semantic externalism. In this paper, I will argue that the same is true of Brueckner’s simple argument and of Brueckner’s disjunctive argument. Although from this it won’t follow that semantic externalism is consistent with the skeptical hypothesis, it will show that it is also not yet decided that it is not