One crucial difference that prevents such scenarios being a direct substitute for the deceiving God and evil demon is that they generally presuppose that we have heads or bodies whereas it is important for Descartes to argue that he can doubt the existence of his body and that he can only be sure he is a 'thinking thing'. Harman's version of the story does, however, add the final thought that having a brain "might be just part of the myth you are being given". See also Allegory of the cave Boltzmann brain Cogito ergo sum Demiurge Dream argument Internalism and externalism Simulated reality Skeptical hypothesis The Imaginary (Sartre) References Further reading — originally published as: Alex Gillespie (2006). Descartes’ demon: A dialogical analysis of ‘Meditations on First Philosophy.’ Theory & Psychology, 16, 761–781. René Descartes Internalism and externalism Demons Concepts in the philosophy of mind Concepts in metaphysics Concepts in epistemology