Reality+: Virtual Worlds and the Problems of Philosophy

by David J. Chalmers

How can we know about reality? This last question was at the heart of the challenge posed by René Descartes in his Meditations on First Philosophy (1641), which set the agenda for centuries of Western philosophy to come. Descartes posed what I’ll call the problem of the external world: How do you know anything at all about the reality outside you? Descartes approached the problem by asking: How do you know that your perception of the world is not an illusion? How do you know that you are not dreaming right now? How do you know you’re not being deceived by an evil demon into thinking all this is real, when it’s not? These days, he might approach the problem by asking the question I just asked you: How do you know you’re not in a virtual world? For a long time I thought I didn’t have much to say about Descartes’s problem of the external world. Thinking about virtual reality gave me a new perspective. It was reflecting on the simulation hypothesis that led me to realize that I had underestimated virtual worlds. In their own way, so had Descartes and many others. I concluded that if we think more clearly about virtual worlds, this might lead us to the beginnings of a solution to Descartes’s problem.