July 28th, 2010

[BLOG-LIKE POSTING] Are we living in a simulated reality?

The question of the reality or unreality of our universe can be traced back at least as far as the famous quote from Zhuangzi ("Now I do not know whether I was then a man dreaming I was a butterfly, or whether I am now a butterfly, dreaming I am a man"), but in our post-Matrix/Inception world the argument has been given its keenest form by the philosopher Nick Bostrom. Bostrom has devoted an entire website, Are You Living in a Computer Simulation?, to his argument in its various iterations and the responses that the argument has gotten and his replies, but I'll borrow from Wikipedia's description for time's sake.

A simplified version of his argument proceeds as such:

i. It is possible that an advanced civilization could create a computer simulation which contains individuals with artificial intelligence (AI).
ii. Such a civilization would likely run many, billions for example, of these simulations (just for fun, for research or any other permutation of possible reasons.)
iii. A simulated individual inside the simulation wouldn’t necessarily know that it is inside a simulation — it is just going about its daily business in what it considers to be the "real world."

Then the ultimate question is — if one accepts that the above premises are at least possible— which of the following is more likely?

a. We are the one civilization which develops AI simulations and happens not to be in one itself?
b. We are one of the many (billions) of simulations that has run? (Remember point iii.)

In greater detail, his argument attempts to prove the trichotomy, either that:

intelligent races will never reach a level of technology where they can run simulations of reality so detailed they can be mistaken for reality (assuming that this is possible in principle); or
races who do reach such a sophisticated level do not tend to run such simulations; or
we are almost certainly living in such a simulation.

I find this rather worrisome since I'm a devotee of the mediocrity principle, the idea that there is nothing special about Earth or humans. If this is the case, then it might be unlikely that our universe isn't a simulation.

Bostrom's argument is practically impossible to prove--even areas of the universe that turned out to be uncomputable might well be within the capabilities of a higher-realm simulator--and so, as the Wikipedia authors conclude, "there is no evidence that can conceivably be produced to show that the universe is not any kind of computer, making the simulation hypothesis unfalsifiable and therefore scientifically unacceptable, at least by Popperian standards."

But who says that Popperian standards are necessarily relevant here? There may not be invisible pink elephants hovering around me, but there is nigh-undetectable dark matter about us all ... Multiple commentators give the Bostrom we-are-in-a-simulation theory a 20% likelihood of actually describing reality.

The interesting thing about the theory that we live in a simulated reality is that it doesn't seem to require that we change our behaviour in any way to accommodate this fact. If our reality is a simulation, it's a good one.

You'll forgive me if I now twitch quietly over there, right?