Oslo Mind, Language and Epistemology Network Seminar: Jonathan Lewis Knowles, Metaphysical realism and semantic externalism

Hilary Putnam is famous for many different philosophical ideas and arguments. Among these are his promotion of semantic externalism (SE) – the idea that meanings are dependent on aspects of speakers’ physical environments that they may be unaware of – and his rejection of metaphysical realism (MR), roughly he idea that our truth-directed thought is ultimately answerable to a world whose nature is thoroughly mind-independent and hence might in principle be quite different from what we take it to be. Though Putnam is also famous for repeatedly changing his mind about what exactly rejecting MR involves, an interesting question that has received little attention in the literature is to what extent SE can be upheld independently of accepting MR, as Putnam clearly seemed to believe was possible. In this paper I will examine this question, starting out with a discussion of a paper by Sandford Goldberg in which he argues that SE does in fact seem to depend on some form of MR. I go on to discuss a response to Goldberg due to Tim Button, as well as a more general line that can be seen as sympathetic to Putnam’s compatibilist position developed by Jussi Haukioja (in part together with Daniel Cohnitz). However, I conclude that there is reason to think Goldberg’s scepticism should be upheld. I finally show how – regardless of exactly what position Putnam exactly held about realism by the end of his life – this conclusion calls for a reinterpretation of his argument that we cannot be (eternal) brains in vats.