Wittgenstein and Putnam: wonderful harmony. The case of brains in a vat

The argument that Hilary Putnam presented in 1981 against the Brains in Vat Hypothesis (BIV) is based on a semantic conception that has close affinities with some of Wittgenstein's reflections on the meaning of linguistic expressions and the nature of mental phenomena presented in the Philosophical Investigations. This has been explicitly acknowledged by Putnam, but there is a fundamental aspect of Putnam's argument against the BIV (an aspect of which Putnam himself was not fully aware) whose origin can also be traced in Wittgenstein - in the latter Wittgenstein, that of Of Certainty. It is in fact centred on the notion of "hinge-proposition". In the article I provide a reconstruction of Putnam's proof against the BIV, I emphasise the links with some passages in the Philosophical Investigations, I highlight the aspect of Of Certainty that makes Putnam's argument work, and I point out how this aspect is already present in the notion of "quasi-necessary truths" developed by Putnam in the 1960s. On the basis of all this, I conclude that the argument against the BIV presented by Putnam in 1981 is correct, despite the criticism to which it has been repeatedly subjected.