[jcranmer]

I like Randall Munroe's summary of the argument (https://what-if.xkcd.com/65/):

> Almost everyone who hears this argument immediately sees something wrong with it. The problem is, everyone thinks it's wrong for a different reason. And the more they study it, the more they tend to change their minds about what that reason is.

[dataflow]

I guess I'm one of those people because I read Wikipedia and this seems like a complete non-sequitur to me:

> The Copernican principle suggests that any one human is equally likely (along with the other N-1 humans) to find themselves in any position n of the total population N.

I feel like I must be misunderstanding the argument because it just doesn't make sense to me. First, why should I even assume N is finite? Second, even if I did, not everyone had an equal chance of participating in this hypothetical thought-experiment (or random selection, or whatever you want to call it) -- only those alive at the time of your sampling can participate in it.

[Denvercoder9]

> First, why should I even assume N is finite?

Our current understanding of physics dictates that the (observable) universe has a finite size and a finite lifespan, from which it logically follows that there can't be an infinite amount of humans.

[dataflow]

If that's genuinely the basis for this reasoning, it only makes the argument seem even more dubious to me. If the statistical argument is really so sound, it shouldn't have to rely on our understanding of cosmology.

Also, is there no phenomenon here where a sufficiently large N becomes increasingly indistinguishable from infinity?

[zeroonetwothree]

The entire universe could very well be infinite, with infinite “Earths” and “humans”. In which case the argument doesn’t work since you can’t choose uniformly from an infinite set.

[zeroonetwothree]

I don’t think the argument is wrong but it has the same problem as any non-repeatable statistical prediction. Namely that you don’t get to repeat it so it’s easy to make an error and hard to calibrate.