Topics Logic

Question Is logic "universal"? For example, when we say that X is logically impossible, we mean to say that in no possible world is X actually possible. But doesn't this mean that we have to prove that in all possible worlds logic actually applies? In other words, don't we have to demonstrate that no world can exist in which the laws of logic don't apply or in which some other logic applies? If logic is not "universal" in this sense, that it applies in all possible words, and we've not shown that it absolutely does apply in all worlds, how can we justify saying that what is logically impossible means the not possible in any possible world, including our actual world?

Accepted:
August 23, 2012

Comments

This is a great question, which deserves a book-length answer. (And in some possible world, perhaps, I would give such an answer.) For many philosophers the 'logically possible' means something like the 'non-contradictory', which (for many) also yields something like the 'limits of intelligibility.' That is, you may imagine the possibility of a world in which logic does not apply, but that is not a world we can grasp, make sense of, in any way. (I can imagine a 'round square' or a 'married bachelor,' I can say those words, but as soon as I try to make sense of such a thing I pretty much have to give up.) So it's not really apparent that we can even meaningfully entertain the notion you're working with, that there are/might be 'possible worlds' in which logic doesn't apply. In light of that it seems plausible to hold, instead, that by 'possible world' we mean 'logically possible world,' i.e. worlds the description of which does not involve any contradicitons (and worlds in which logic is applicable). So we don't have to 'demonstrate' that the laws of logic apply -- we stipulate that they do, as a cost for speaking or thinking intelligibly ....

just a start of an answer, but possibly it's helpful ....

I don't understand the question, because I don't understand the phrase 'a world in which the laws of logic don't apply'. I don't think any sense can be attached to that phrase. Is a world in which the laws of logic don't apply also a world in which they do apply? If no, why not? If yes, is that same world also a world in which the laws of logic neither apply nor don't apply? If no, why not? It's as if the questioner had asked, "Don't we have to demonstrate that no world can exist in which @#$%^&*?"