ZQrn
Well, it depends on how you define '->' for multi valued logics.
I mean, say we have a logic where every truth value is in [0,1], surely I could then define P -> Q such that P <= Q.
I'm sure we could still derive some interesting things from it.
But I kind of have to plead ignorance on multi valued logics here, so maybe you have a superb reason on why this can't be done.