Last week, the famous Tesla and SpaceX CEO and PayPal cofounder Elon Musk said that he is almost certain that we are living in a sim -- that is, that we are basically just artificial intelligences living in a fictional environment in someone else's computer.
The basic argument, adapted from philosopher Nick Bostrom, is this:
1. Probably the universe contains vastly many more artificially intelligent conscious beings, living in simulated environments inside of computers ("sims"), than flesh-and-blood beings living at the "base level of reality" ("non-sims", i.e., not living inside anyone else's computer).
2. If so, we are much more likely to be sims than non-sims.
One might object in a variety of ways: Can AIs really be conscious? Even if so, how many conscious sims would there likely be? Even if there are lots, maybe somehow we can tell we're not them, etc. Even Bostrom only thinks it 1/3 likely that we're sims. But let's run with the argument. One natural next question is: Why think we are in a large, stable sim?
Advocates of versions of the Sim Argument (e.g., Bostrom, Chalmers, Steinhart) tend to downplay the skeptical consequences: The reader is implicitly or explicitly invited to think or assume that the whole planet Earth (at least) is (probably) all in the same giant sim, and that the sim has (probably) endured for a long time and will endure for a long time to come. But if the Sim Argument relies on some version of Premise 1 above, it's not clear that we can help ourselves to such a non-skeptical view. We need to ask what proportion of the conscious AIs (at least the ones relevantly epistemically indistinguishable from us) live in large, stable sims, and what proportion live in small or unstable sims?
I see no reason here for high levels of optimism. Maybe the best way for the beings at the base level of reality to create a sim is to evolve up billions or quadrillions of conscious entities in giant stable universes. But maybe it's just as easy, just as scientifically useful or fun, to cut and paste, splice and spawn, to run tiny sims of people in little offices reading and writing philosophy for thirty minutes, to run little sims of individual cities for a couple of hours before surprising everyone with Godzilla. It's highly speculative either way, of course! That speculativeness should undermine our confidence about which way it might be.
If we're in a sim, we probably can't know a whole lot about the motivations and computational constraints of the gods at the base level of reality. (Yes, "gods".) Maybe we should guess 50/50 large vs. small? 90/10? 99/1? (One reason to skew toward 99/1 is that if there are very large simulated universes, it will only take a few of them to have the sims inside them vastly outnumber the ones in billions of small universes. On the other hand, they might be very much more expensive to run!)
If you/I/we are in a small sim, then some version of radical skepticism seems to be warranted. The world might be only ten minutes old. The world might end in ten minutes. Only you and your city might exist, or only you in your room.
Musk and others who think we might be in a simulated universe should take their reasoning to the natural next step, and assign some non-trivial credence to the radically skeptical possibility that this is a small or unstable sim.
"Skepticism, Godzilla, and the Artificial Computerized Many-Branching You" (Nov 15, 2013).
"Our Possible Imminent Divinity" (Jan 2, 2014).
"1% Skepticism" (forthcoming, Nous).