Scepticism in the <i>Tractatus</i> and in <i>On Certainty</i>

Contrary to Moore, Wittgenstein does not believe that a ‘theoretical’ sceptical doubt can be ‘refuted’ – i.e., proven to be false, as it also cannot be proven to be true. Interestingly, this is an idea that Wittgenstein never really changed his mind about, as already in the Tractatus we find him say: ‘Scepticism is not irrefutable, but obviously nonsensical, when it tries to raise doubts where no questions can be asked.’ In this contribution, I will explain why Wittgenstein thinks that scepticism is ‘obviously nonsensical’ and what light this can throw on the anti-sceptical strategy that Wittgenstein develops later in On Certainty. I conclude by comparing my proposal to two others in the literature (Moyal-Sharrock’s and Williams’).