Tuesday, August 14, 2007

Living in a simulation

This NY Times article discusses the possibility that we live in a simulation. It's an old idea, but one you have to take seriously if you believe in a technological singularity.

I discussed this in an earlier post, string landscape, AI and virtual worlds, in which I decried the latest anthropic fad in theoretical physics:

...let me now turn to a reductio ad absurdum of anthropic arguments.

Let R = the ratio of number of artificially intelligent virtual beings to the number of "biological" beings (humans). The virtual beings are likely to occupy the increasingly complex virtual worlds created in computer games, like Grand Theft Auto or World of Warcraft (WOW will earn revenues of a billion dollars this year and has millions of players). In the figure below I have plotted the likely behavior of R with time. Currently R is zero, but it seems plausible that it will eventually soar to infinity. (See previous posts on the Singularity.)

If R goes to infinity, we are overwhelmingly likely to be living in a simulation...

Think of the ratio of orcs, goblins, pimps, superheroes and other intelligent game characters to actual player characters in any MMORPG. In an advanced version, the game characters would themselves be sentient, for that extra dose of realism! Are you a game character, or a player character? :-)

By the way, the author of the article John Tierney gives the simulation idea a probability P of greater than 50%, while Bostrom, the Oxford philosopher who apparently thinks about this stuff as his day job, gives it about 20%. To me it's not implausible, but keep in mind: if you are *inside* the simulation your local conditions in principle tell you nothing about the outside world in which the simulation runs. So, we basically know nothing about P unless (1) we just happen to be in a realistic historical simulation or (2) we haven't yet hit the singularity. (2) is of course highly unlikely if R does go to infinity -- we'd be in a very special subset of sentient beings. So I'd say it's unlikely that our estimate of P is very good.

NYTimes: ...Dr. Bostrom assumes that technological advances could produce a computer with more processing power than all the brains in the world, and that advanced humans, or “posthumans,” could run “ancestor simulations” of their evolutionary history by creating virtual worlds inhabited by virtual people with fully developed virtual nervous systems.

Some computer experts have projected, based on trends in processing power, that we will have such a computer by the middle of this century, but it doesn’t matter for Dr. Bostrom’s argument whether it takes 50 years or 5 million years. If civilization survived long enough to reach that stage, and if the posthumans were to run lots of simulations for research purposes or entertainment, then the number of virtual ancestors they created would be vastly greater than the number of real ancestors.

There would be no way for any of these ancestors to know for sure whether they were virtual or real, because the sights and feelings they’d experience would be indistinguishable. But since there would be so many more virtual ancestors, any individual could figure that the odds made it nearly certain that he or she was living in a virtual world.

The math and the logic are inexorable once you assume that lots of simulations are being run. But there are a couple of alternative hypotheses, as Dr. Bostrom points out. One is that civilization never attains the technology to run simulations (perhaps because it self-destructs before reaching that stage). The other hypothesis is that posthumans decide not to run the simulations.

“This kind of posthuman might have other ways of having fun, like stimulating their pleasure centers directly,” Dr. Bostrom says. “Maybe they wouldn’t need to do simulations for scientific reasons because they’d have better methodologies for understanding their past. It’s quite possible they would have moral prohibitions against simulating people, although the fact that something is immoral doesn’t mean it won’t happen.”

Dr. Bostrom doesn’t pretend to know which of these hypotheses is more likely, but he thinks none of them can be ruled out. “My gut feeling, and it’s nothing more than that,” he says, “is that there’s a 20 percent chance we’re living in a computer simulation.”

My gut feeling is that the odds are better than 20 percent, maybe better than even. I think it’s highly likely that civilization could endure to produce those supercomputers. And if owners of the computers were anything like the millions of people immersed in virtual worlds like Second Life, SimCity and World of Warcraft, they’d be running simulations just to get a chance to control history — or maybe give themselves virtual roles as Cleopatra or Napoleon. ...


Anonymous said...

How can we reconcile this with the Doomsday argument, though?

Steve Hsu said...

I don't see any contradiction. If we live in a simulation we are *typical* of the most common type of sentient being (artificial). That is consistent with Gott's hypothesis that we *do not* live at a special time (i.e., the first or last 2.5% of human history). Of course, if we are in a simulation what we see around us may have little to do with actual human history.

Douglas Natelson said...

Gott is a fantastic classroom teacher, btw.

Sometimes I think I'm the only person who has realized why the Singularity won't happen: society is not stable if god-like technology is granted to all (or even a large number) of its members. Think about it: if you gave, say, 10% of the world's population their own nuclear weapons or bioweapons, do you think civilization is a stable fixed point? As individual capabilities grow, all it takes is a small number of individuals to make the whole world unhappy. Modern terrorists are a great example of this.

A.R.Yngve said...

I worked for years as a QA in the software industry...

... and I have this pet theory: people with a background in programming have a tendency to overrate the power of programming. It's no coincidence that writers who visualize awesome computing are into computers. The-World-Is-A-Simulation is the coder's wet dream.

People with a background in QA have a tendency to think that all programs are flawed and will crash. Therefore I cannot believe that this world is a simulation: IT DOESN'T CRASH.

Steve Hsu said...

Do you think an orc in WOW knows how often the system crashes? :-)

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