 David Lewis, one of the main proponents of four-dimensionalism, suggests that the principal reason to accept the view is to solve what he calls “the problem of temporary intrinsics”. How can a single thing—Lewis, for example—have different intrinsic properties—like being straight, while he is standing, and then being bent, while seated—at different times? Not by standing in different relations—the being straight at and being bent at relations—to different times, he argues. (Since, he says, being straight and being bent are genuine properties rather than disguised relations.) And not in virtue of there being only one reality—such as the time when Lewis is bent—so that reality consists of Lewis, and every other thing, being the way it is now and not any other way. (For Lewis points out that we all believe we have a past and a future, in addition to a present.) So Lewis suggests that the best answer to the question about how a single thing can have different intrinsic properties at different times is that such an object has different temporal parts which themselves have the different intrinsic properties.