Abstract
This chapter develops the issue of external world skepticism in a stunning new direction, suggesting that virtual reality science fiction thought experiments depict science fact. The author has authored an influential argument that we are, in fact, in a computer simulation. He observes that assuming that a civilization survives long enough to be technologically sophisticated, it would likely be very interested in running simulations of entire worlds. The core of the simulation argument shows that we should accept as true at least one of the following three propositions: the chances that a species at our current level of development can avoid going extinct before becoming technologically mature is negligibly small; almost no technologically mature civilisations are interested in running computer simulations of minds like ours; and a person is almost certainly in a simulation.