Abstract: Simulation Theory says we need not rely exclusively on prepositional knowledge of other minds in order to explain the actions of others. Seeking to know what you will do, I imagine myself in your situation, and see what decision I come up with. I argue that this conception of simulation naturally generalizes: various bits of our mental machine can be run‘off-line’, fulfilling functions other than those they were made for. In particular, I suggest that visual imagery results when the visual system is run off-line. I briefly review the empirical evidence and consider the philosophical implications, particularly concerning the mode of mental representation in imagery.