Bostrom's Trilemma (2003)
Published in the Philosophical Quarterly. If any civilization reaches the ability to run ancestor simulations, and chooses to do so, then simulated realities vastly outnumber base reality. The probability that we are in base reality may be vanishingly small. One reading is that the only escape is to claim that civilizations never reach simulation capability, or that they always choose not to run simulations.
Source: Bostrom, N. (2003). “Are You Living in a Computer Simulation?”Philosophical Quarterly, 53(211), 243–255.