Can a Sadistic Torturer Be Convicted of Irrationality?

There is one main reason why we might want to convict a sadistic torturer of irrationality, and that is a "contemporary form of the Kantian hope" that morality is intrinsically tied to our capacity to reason, because we might like to think that to act immorally is to act irrationally. Bernard Williams has argued that this hope is misguided and that morality is not tied to reason in this way, so we cannot convict a sadistic torturer of irrationality. John McDowell, on the other hand, has argued that we may indeed convict a sadistic torturer of irrationality. In this essay I will argue, with Williams, that morality and rationality are not quite tied together in the way outlined above. I will consider Christine Korsgaard's neo-Kantian approach as a bridge between Williams' and McDowell's views, and argue that, whilst we cannot convict a sadistic torturer of irrationality, we can convict him of inconsistency or, in some cases, of arationality.