This lecture deals with philosophical scepticism about the physical world. This is the idea that we do not really have any evidence (at all!) for any of our ordinary beliefs about the world around us, because we cannot rule out the possibility that all our experience is some sort of massive illusion. We look at the detail of the argument for this startling view, and at one of the responses that may be made to it. The lecture refers to Chapter 3, "Brain-Snatched", in Stephen Law's book, The Philosophy Gym. Copyright 2013 Jack Reynolds / La Trobe University, all rights reserved. Contact for permissions.