 Thus, backward causation demands eternalism or a static account of time in the sense that there is no objective becoming, no coming into being such that future events exist on the par with present and past events. It means that the future is real, the future does not merely consist of unrealised possibilities or even nothing at all. Ordinarily we may think of the past as a nothing that once was a something. But when asked what makes sentences about the past true or false, we would probably also say that it is the facts of the past that make present sentences about the past either true or false. The fact that I went to the cinema yesterday makes it true today when I say that I went to the cinema yesterday. This view is a realist one with respect to the past. If backward causation is to be conceptually possible, it forces us to be realists with respect to the future. The future must contain facts, events with certain properties, and these facts can make sentences about the past/future true or false. Such a realist account is provided by static and tenseless theories of time. Eternalism is such a theory and holds that the participation of time into the past, the present and the future depends on the perspective we human beings put on the world. The attribution of pastness, presentness and futureness to events is determined by what we take to exist at times earlier than and times later than the time of our experience. (For further discussion, see the entry on   being and becoming in modern physics.)