Logic

If something logically exists (or logically does not exist) in one possible world, why is it necessary for that same something to logically exist (or logically not exist) in all possible worlds? I do not have any background in modal logic and I am trying to understand the argument for the nonexistence of time as described in Yourgrau's recent book on Gödel and Einstein.

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Suppose we know through logic alone that something is true about the world. I don't know if there are such truths (or even such ways of knowing), but a good candidate might be the claim that no state of affairs simultaneously holds and doesn't hold of the same portion of the world. If considerations of pure logic (assuming there is such a thing) show us that this is really true of the world then they also seem to show that it is true of any possible world--any way that the world might have been. Changing the world's details, and even its physical and metaphysical laws wouldn't seem to affect the status or applicability of logic itself, or of any truths that might follow from it.

That seems like a reasonable inference, but I haven't, alas, read Yourgrau's book, and so can't apply it to the existence of time. But maybe someone else can...

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