 Persistence. What does it take for a person to persist from one time to another—to continue existing rather than cease to exist? What sorts of adventures is it possible, in the broadest sense of the word ‘possible’, for you to survive, and what sort of event would necessarily bring your existence to an end? What determines which past or future being is you? Suppose you point to a child in an old class photograph and say, “That’s me.” What makes you that one, rather than one of the others? What is it about the way she relates then to you as you are now that makes her you? For that matter, what makes it the case that anyone at all who existed back then is you? This is sometimes called the question of personal identity over time. That’s because it’s about whether the earlier being and the later being are one or two—that is, whether they are numerically identical. An answer to it is an account of our persistence conditions.