Say you scroll out all possible worlds before God and he actualizes Q. What happened?
1.) Did one possible world choose another? This can’t be right, since as possible it can’t do anything.
2.) Did something in no possible world make a possible world actual? But, on the PW scheme, this means that something impossible happened.
3.) Did the actual world choose a possible one? But qua actual it is either other than a possible world or not. If other, we get #2; if not, #1.
4.) Is Q the same as God’s actual world or not? Not the same, since one can’t actualize what is already actual. Not other, since we can’t have two things fitting the description of “the actual world”, leaving us to say, for example, that God exists and does not exist in the actual world.
There are tensed statements in possible worlds. Therefore there is one actual clock for all of them. But there isn’t even one clock for us, so there are no tensed statements in possible worlds. So by PW logic, tensed statements are impossible. Therefore this could not have been written.