What? All of them?
First define your raven. Today's problem is about claiming all x are y and proving the assertion to be so. The declaration is that "All ravens are black". The philosopher gets out of trying to prove the claim by defining ravens as black and essentially denying any black bird of the corvida species is a raven. As someone points out, what happens if the raven catches a disease which turns it green temporarily? Is it still a raven during that time? I guess there are two problems. One is how to prove that all instance of x are y whether they're dead, alive, or yet to come; the other is a matter of definition, because if something ceases, at least for a time, to satisfy a definition, does it cease to be that thing? Oh, ah. According to the discussion, we're into the world of a priori vs. a posteriori which (and I hate these terms, to be honest, and understand them vaguely at best) are basically behind the whole rationalist vs. empiricist debate. I suppose with t...