It is especially tempting to accept Presentism if one already thinks that reality is dynamic. For it is natural to think that, as the future becomes present, it comes to be: it becomes a part of reality. And, conversely, it is natural to think that, as the present slips into the past, it ceases to be: it ceases to be a part of reality. Presentism is often contrasted with Eternalism, according to which reality includes the past and the future as well as the present. Eternalists have to account for the dynamic nature of reality in some other way or deny that reality is dynamic.2 One consequence of Presentism is that the only things that reality includes are things that presently are. For example, according to Presentism, if Plato no longer exists and the first philosopher to be born in the twenty-third century doesn’t exist yet, then they aren’t parts of reality; but, given that Saul Kripke does exist now, he is a part of reality. (He’s a part of reality now; but—given that he didn’t exist a hundred years ago and won’t exist a hundred years from now—he wasn’t a part of reality a hundred years ago and he won’t be a part of reality a hundred years from now.) Another consequence of Presentism is that the only instantiations of properties and...