Have you ever wondered—even if just for a second—whether we might all be in the "Matrix," hooked up to machines and fed a non-stop computer-generated illusion? Or maybe we’re in a version of The Truman Show, where the objects we see are real but the people are just actors pretending to be our friends. How we could ever know for sure? What’s to say you’re not a figment of my imagination, cunningly crafted by our robot overlords? What's to say I'm not a figment of your imagination?

It's true that I don’t feel like a figment of your imagination. And Descartes, of course, famously argued that as long as you're doubting—even doubting the reality of everything you can see, hear, and touch!—you're still thinking, and thinking shows you exist. (Cogito ergo sum, and all that.) Plus Descartes went on to claim that since God is good, we can trust most of what our senses tell us. But along the way, Descartes offered one of the all-time awesome skeptical thought experiments, one that's a pretty good precursor of The Matrix. 

What if there's an evil demon out there, and he's casting a spell on you at all times, making you believe there are chairs and tables and flowers and trees when in fact there's nothing, or something quite different? We would always be deluded... and we would never be able to know. That's a scary thought.

You might respond by saying demons aren't real, which—fair enough. But imagine a world two hundred years from now. Presumably we’ll have computers of unimaginable power, along with AI and VR up the wazoo. We’ll hopefully have solved our energy problems, and have virtually unlimited processing power. There will be a bunch of people with copious spare time (perhaps after being laid off by GPT-7500). Why not think that some of them will use that spare time to run fancy simulations—making Martian palaces, reliving Pride and Prejudice, or even simulating Philosophy Talk from the year 2023? According to Hans Moravec, that's what makes it so likely that we are all actually sims. Ray and Josh included.

Josh and Ray might want to argue that those sims would just be knock-offs, not the real Josh and Ray—but then again, isn't that exactly what a pair of sims would say? Think about it: those future programmers won’t just make one simulation of 2023; they’ll make thousands. So the chances that the hosts are the originals are actually vanishingly small.

Then again... who would want to make thousands of simulations of a couple of philosophers on the radio?

Maybe our guest will convince us that we’re already in a simulation—or at least that we can't discount the possibility. It’s David Chalmers from NYU, author of Reality+: Virtual Worlds and the Problems of Philosophy. We, or our virtual-world avatars, are looking forward to it.