chapter  9
Pages 21

G.E.Moore’s ‘A Defence of Common Sense’ was first published in 1925 and his ‘Proof of an External World’ fourteen years later.2 Apparently Wittgenstein had a long-standing interest in these papers and in the last eighteen months of his life, stimulated3 by discussions with Norman Malcolm while his house-guest in Ithaca in 1949, he composed the notes we now have as On Certainty. My question here is whether Wittgenstein’s last philosophical thoughts point to a principled and stable response to the issue at which Moore’s papers had been directed-the issue of scepticism, and particularly scepticism about our knowledge of the material world. My eventual and hesitant answer will be: yes, though the development here will be inevitably sketchy. And it will be focused upon one specific-though as disturbing as any, and very general-form of sceptical argument, which I shall begin by eliciting, ironically, from the consideration of something that was supposed to help-Moore’s curious ‘Proof’ itself.