In this video from TED-Ed, James Zucker teams up with Stretch Films' John R. Dilworth to dish out a cogent, three-minute introduction to René Descartes' Meditations on First Philosophy. If you've ever wondered how to get from "How do I know I'm real?" to "I think, therefore I am," this one's for you.

Complement with Nick Bostrom's argument for simulated existence: