The main motivation of the foundationalist view is to save knowledge from sceptical doubt. This chapter maintains that such motivation is unjustified. Indeed, according to a widespread opinion, absolute scepticism is irrefutable, since no logical argument can be advanced against it. On the contrary, the chapter argues that logical arguments can be advanced against all sceptical doubts raised since antiquity. It would be impossible to show this for all such sceptical doubts in a limited space. Nevertheless, the chapter shows it for some of the main ones, specifically, the sceptical doubts raised by two schools discussed by Aristotle, Sextus Empiricus' indeterminacy doubt, Descartes' dream doubt, Descartes' demon doubt, and Hume 's induction doubt. The chapter also argues that, contrary to the widespread opinion that absolute scepticism stands on the side of logic and reason, absolute scepticism stands on the side of mysticism.