The dominant view, though, is that reality is outside your mind. To be real, you need something more than just appearances; you need some underlying powers or potentiality. The great Australian philosopher Samuel Alexander said, “To be real is to have causal powers” — if you can be something that actually makes a difference. Phillip K. Dick once said, “A real thing is something that doesn’t go away when you stop believing in it.” If you’ve got something that is independent of your mind, which has causal powers, which you can perceive in all these ways, to me you’re a long way toward being real.

Things in virtual realities, at least in principle, have all those properties. Say you’re in a virtual world. There are objects there that you can perceive around you. In a virtual world a virtual tree can fall even if I’m not around. A virtual tree has causal powers. A virtual tree falling can cause people to have experiences. It can break something that it falls on in the virtual world, and it can be experienced. Virtual reality is just a different form of reality. But it’s still perfectly real.

P.R.: Why do you think the original intuition on this topic was precisely the opposite, that virtual reality is nothing but instantiated fantasy?

D.C.: This goes back a long way in the history of philosophy. René Descartes said, “How do you know you’re not being fooled by an evil demon right now into thinking this is real when none of it’s real?” Descartes’ evil-demon question is kind of like the question of a virtual reality. The modern version of it is, “How do you know you’re not in the matrix? How do you know you’re not in a computer simulation where all this seems real but none of it is real?” It’s easy for even a movie like “The Matrix” to pump the intuition in you that “this is evil. This isn’t real. No, this is all fake.”

The view that virtual reality isn’t real stems from an outmoded view of reality. In the Garden of Eden, we thought that there was a primitively red apple embedded in a primitive space and everything is just as it seems to be. We’ve learned from modern science that the world isn’t really like that. A color is just a bunch of wavelengths arising from the physical reflectance properties of objects that produce a certain kind of experience in us. Solidity? Nothing is truly solid out there in the world. Things are mostly empty space, but they have the causal powers to produce in us the experience of solidity. Even space and time are gradually being dissolved by physics, or at least being boiled down to something simpler.

Physical reality is coming to look a lot like virtual reality right now. You could take the attitude, “So much the worse for physical reality. It’s not real.” But I think, no. It turns out we just take all that on board and say, “Fine, things are not the way we thought, but they’re still real.” That should be the right attitude toward virtual reality as well. Code and silicon circuitry form just another underlying substrate for reality. Is it so much worse to be in a computer-generated reality than what contemporary physics tells us? Quantum wave functions with indeterminate values? That seems as ethereal and unsubstantial as virtual reality. But hey! We’re used to it.

P.R.: I’m wondering whether it’s useful to say that virtual reality isn’t simply an alternate reality but is rather a sub-reality of the one we normally occupy.