 A third argument, against the possibility of time travel to the past, has to do with the claim that backward causation is impossible. For if there can be no backward causation, then it is not possible that, for example, your pushing the button in your time machine in 2020 can cause your appearance, seemingly out of nowhere, in, say, 1900. And yet it seems that any story about time travel to the past would have to include such backward causation, or else it would not really be a story about time travel.