We can only perceive (although this represents most people's conception of reality) a simulation constructed by our sensory organs. We do not know if reality indeed exists out there somewhere, the fact remains that there need be none. Although I hate to bring up a post-Cartesian vision of the brain in a vat hooked up to a machine which keeps feeding sensory input to it, that might indeed be the case. When we dream, for instance, do we experience reality or not? When we talk about fiction based on real life, for instance, should that fiction be considered real or simulated? Questions, questions...