If the A-theory of time is true, then it is (metaphysically) possible that the year 2010 have the objective property P of presentness and it is also possible that the year 2019 have P. For it is true that 2019 has P, and what is true is possible. But by the same token in 2010 it was true that 2010 has P, and so it was possible that 2010 have P. And what is metaphysically possible does not change. So even now it is possible that 2010 have P.
But a proposition is possible if and only if it is true at some possible world. Thus, if the A-theory of time true, there are possible world where 2010 has P and possible worlds where 2019 has P, and in 2010 we lived in one of the worlds where 2010 has P, while now in 2019 we instead live in a world where 2019 has P.
Consequently, given the A-theory of time, what world we inhabit continually changes.
This seems counterintuive. For now it looks like caring about what will happen is caring about what happens in some merely possible world.
Alex
ReplyDeleteNow in 2019, we live in a world where 2019 has P means that we live in a world where P is actual in 2019 and P was actual in 2010 and P will be actual in 2031.
The world in 2010 was: P is actual in 2010 and P will be actual in 2019 and P will be actual in 2031.
Of course, given the A-theory, we live in a world that continually changes, because that's essential to the A-theory: every temporal world changes because which elements of the world are actualized depends on the time.
But that doesn't mean that, according to A-theory, we move between possible worlds
If we drop the time reference we go from "in our world (wO)P is actual in 2019 and P was actual in 2010 and P will be actual in 2031" to "in wO P is true in 2010, 2019 and 2031". Both are descriptions of the same possible world from a different point of view but they do not entail moving from one possible world to another.