http://en.wikipedia.org/wiki/Raven_paradox
my solution:
  in the statement that everything that is not a raven is not black, "everything" is not actually a closed set. for our purposes, it's a an unlimited open field. observing that the green apple is not a raven is (almost) equivalent to adding a new item to the set on the spot that is a non-black non-raven. if we added a non-black raven to the set on the spot, yes, that would be evidence (against), but we can't actually do that because ravens are defined as black. the statement is inductive, but once you start deriving other statements from it you lose track of its falculty of a non-definition. that's why it seems meaningless to introduce the evidence that a green apple, which is unrelated to ravens, is not black. it's unrelated to whether ravens are black by definition.
"i think it's true that all ravens are black"
if you translate that to "i think it's true that everything that is not a raven is not black", then maybe the green apple is actually evidence.
maybe the open question is whether "i think it's true that all ravens are black" is actually equivalent to "i think it's true that everything that is not a raven is not black."
it's already been shown via other paradoxes that not all rules of deduction apply to belief statements.
a further ambiguity is that in "i think it's true that everything that is not a raven is not black" it is not clear whether we thnik that we may find a counterexample or that we think that everytihng that is not a raven is not black by definition.
furthermore, saying that everything that is not a raven is not black doesn't tell us whether there is anything that is a raven or anything that is black. it also doesn't tell us if all ravens are black. it could be true that some ravens are white, but all non-ravens are also white. if everything is the collection of things in reality, tehre aren't necessarily black non-ravens. if everything is all possible imaginable things, then it includes black non-ravens, but observed things like a green apple are not evidence in that case.