Forty-five years ago, cosmologist Brandon Carter postulated that no observer should expect to find that he or she had come into existence exceptionally early in the history of his or her species. “Suppose you know that your name is in a lottery urn,” writes philosopher John Leslie, “but not how many other names the urn contains. You estimate, however, that there’s a half chance it contains a thousand names, and a half chance of its containing only ten. Your name then appears among the first three drawn from the urn.