The whole “reality is an illusion” idea has been kicked around by everyone from Siddhartha to the existentialists. It is Oxford philosopher Nick Bostrom who is most often associated with the idea that we are living in a computer simulation. His premise is based on a series of assumptions:
1). A technological society could eventually achieve the capability of creating a computer simulation that is indistinguishable from reality to the inhabitants of the simulation.
2). Such a society would not do this once or twice. They would create many such simulations.
3). Left to run long enough the societies within the simulations would eventually be able to create their own simulations, also indistinguishable from reality to the sub-simulations inhabitants.
As a result, you have billions of simulations, with a nearly infinite number of cascading sub-simulations, all of them perfectly real to their inhabitants. Yet there is only a single ultimate progenitor society. The math is actually pretty simple: the odds are nearly infinity to one that we are all living in a computer simulation. –io9. We come from the future..