He did the math.

In an influential 2003 paper, University of Oxford philosopher Nick Bostrom laid out the possibility that our reality is a computer simulation dreamed up by a highly advanced civilization. In the paper, he argued that at least one of three propositions must be true:

1. Civilizations usually go extinct before developing the capability of creating reality simulations.
2. Advanced civilizations usually have no interest in creating reality simulations.
3. We’re almost certainly living inside a computer simulation.

Now, Columbia University astronomer David Kipping took a hard look at these propositions, also known as Bostrom’s “trilemma,” and argued that there’s essentially a 50-50 chance that we are indeed living in a simulation, Scientific American reports.

Kipping collapsed the first two propositions into one, arguing that they both would result in the same outcome — we are not living inside a simulation.

“You just assign a prior probability to each of these models,” Kipping told SA. “We just assume the principle of indifference, which is the default assumption when you don’t have any data or leanings either way.”