Putnam’s Proof against Radical Skepticism: Two Reinterpretations Grounded in Self-Knowledge

Abstract

I present and defend two reinterpretations of Putnam’s proof that we are not brains in a vat. Both of them make explicit the role played in it by self-knowledge of our own thoughts and the role played by content externalism. The first one takes externalism as implying that a brain in a vat cannot have the relevant content (involving concepts about brains and vats). The other version only extracts from externalism a weaker thesis that a bodily subject and a brain in a vat cannot share the relevant content.