In the last few decades, analytic philosophers have taken an interest in the sort of transcendental scepticism associated with the figure of the malign demon in Descartes’ Meditations. Rather than invoke a being with religious or superstitious overtones, recent philosophers, starting with Peter Unger’s Ignorance (1975), have expressed the sceptical challenge in terms of a supposed mad scientist who is manipulating a brain – mine – to produce in me states that are not experientially distinguishable from the states in which I would find myself if I were not a brain in a vat. The first part of the discussion seeks to trace the spread of the mad scientist as the surrogate of Descartes’ demon and to observe two effects of this modernising move. The first of these can be found in the efforts made to refute the apparent possibility that I am a brain in a vat manipulated by a mad scientist (Putnam 1981, Nozick, 1981). And the second is the tendency to take for granted an equivalence between a physical object – my brain – and the object that the Cartesian narrator says he is investigating: his experience, about whose physical realisation he says he is in the dark. We then pass to show how what has become the orthodox exegesis, in recent Anglophone philosophy from Kemp Smith (1952) and Beck (1968) through Kenny (1968), Williams (1978) and Curley (1980) down to Secada (2000), attributes to Descartes some effort to refute the apparent possibility that I am the victim of a malign demon. The orthodoxy of this attribution may be cause or effect of the concurrent tendency to believe that it is necessary to exclude the apparent possibility of the mad scientist in order to make the world safe from the threat of transcendental scepticism. In the light of an examination of the dynamics of Descartes’ text, we see that it is neither necessary nor possible to exclude the demon, and we consider the suggestion that the knowledge that the Cartesian project sets itself to uncover is of a wholly different kind from the supposed knowledge that really is threatened by the demon/scientist. The final position seems to be that what remains under threat from the demon/scientist is the sort that recent philosophers have called ‘empirical knowledge’. Though many philosophers, beginning perhaps with Kant (1787), have thought it a ‘scandal’ that empirical knowledge cannot be made safe from transcendental scepticism, it is not at all clear why we should be scandalised.