Time may be infinite in both directions. If it is, then, if persons could live at most once in all of time, the probability that you would be alive now would be zero. Since you are alive now, with certainty, either the past is finite, or persons can live more than once.
cl0ud: The probability that you are alive at any given time is the total time that you are alive, say 80 years, divided by the total amount of time. So if the total amount of time is ∞, then the probability that you are alive at any given time is 80/∞ = 0.
You really have to read the whole paper to get the argument though.
slowtyper237: you are right that 1/∞ and n/∞ are the same but Huemer suggests we live infinitely many times.
Nothing I think, since probability has to be asymptotic to zero and not zero exactly. Because if it was zero exactly then nothing would happen in infinite time. 1/infinity and n/infinity are pretty much the same thing. Whether we can live more than once or not is therefore still unknown, and as unlikely as us getting to exist at all.