Are you a Sim?

After watching The Matrix, a lot of us enjoy flirting with the idea that we might be in some kind of simulation. Oxford philosopher Nick Bostrom suggests that this shouldn't be a mere flirtation. He argues that the odds that you are right now living in a computer simulation are pretty good. There's a website dedicated to the presentation and discussion of "the simulation argument." A short version of it can be found here.

Essentially, Bostrom argues that one of the following three claims must be true:

1. Almost all civilisations at our level of development become extinct before becoming technologically mature.

2. The fraction of technologically mature civilisations that are interested in creating ancestor simulations is almost zero.

3. You are almost certainly living in a computer simulation.

To the extent that you're inclined to think that 1 and 2 are false, then, you'd be justified in thinking that 3 is true.

Or, to put it another way, if a civilization advances to the point where they're capable of providing simulated environments, and if that civilization is interested in running simulations of the past (ancestor simulations), then there will be many people living in such simulations. And if the set of persons contains a significant number of people in simulations, there's at least some significant probability that you are such a person!

It's not an easy argument to assess. What do you think?