If we posit a second temporal dimension then changing the past amounts to making some time one way at one location in meta-time, and some other way at some other location in meta-time.
We can now at least make sense of how a time could change.
It’s easy to see why these storylines are captivating.
They ask us to imaginatively entertain questions about the robustness of the present.
At least, no time exists at more than one time in the same temporal dimension.
If we were to introduce a second temporal dimension – sometimes called meta-time – then a single time in one temporal dimension could exist at multiple times in a second temporal dimension.Suppose that on Monday at 2 pm Annie’s mass is 21.2 kgs (Annie is a dog). She won’t do this by trying to make her mass different at Monday at 2 pm.Instead, she will try and make her mass at times later than Monday at 2 pm, less, or more, than 21.2 kgs.The “first way” the time is (the pre-change way) is how that time is at one time in meta-time.The “second way” the time is (the post-change way) is the way the time is at some other time in meta-time.So if erasing certain past events and replacing them with new events, is what changing the past would amount to, then even were there a second temporal dimension, we still could not change the past.So far this makes it sound as if philosophers are a bunch of science fiction spoil sports. Although philosophers typically agree that we cannot change the past, most think it possible to causally affect the past. Changing is altering a time from being one way, the first time around, to being some other way, the second time around (hence “the second time around fallacy”).Causally affecting a time is making a time the way that, in fact, it is.If anyone travels to the past they will causally affect the time to which they travel: they will breathe air, tread on bugs, talk to people, and so on.We are asked to ponder to what extent the way things are now is the product of fluky events, so that had the past been ever so slightly different, the present would be very different indeed.These questions are intriguing because we all wonder to what extent our present selves are the result of choices we made, where we could so easily have made others, and to what extent who we are is most robust, resilient under small changes in our past decisions.