How do we know the world is real? There’s the evidence of our five senses—sight, taste, touch, smell and hearing—but can’t those responses be hijacked or simulated? Such questions have preoccupied thinkers for millennia, from the speculations of ancient religious texts and philosophers like René Descartes, to paranoid science fiction novels, television and blockbuster films. A kaleidoscopic deep dive down the rabbit hole of “simulation theory,” A Glitch in the Matrix is the mind-bending, exhilarating, and definitive introduction to a subject that, subscribe to it or not, involves us all. Directed by Rodney Ascher (Room 237, The Nightmare), the preeminent documentarian of today’s obsessional thinking, A Glitch in the Matrix introduces us to a handful of real-world testifiers who are certain that their bodies and minds are being operated by some external game-player.