Persistence
Regardless of whether the future or past are real, there is also the question of what objects are. What is it for an object to persist in time? At one time, one is short and at another time tall. Is something a four-dimensional object with different temporal parts? Or is there a wholly present three-dimensional entity that changes properties? This chapter gives a survey of this problem, updating three positions on it to the relativistic context, and providing the reader with a solid base from which to evaluate the positions. It notes that people recognize the problem of persistence as being primarily about parthood and location, and also sketches views known as three-dimensionalism (3Dism) or endurantism, and four-dimensionalism (4Dism) or perdurantism.