So now. We're reading a few people who tried to get around that, and one of them gives the instantial model, which I don't feel like getting into. Essentially it says that any instance which agrees with an induced conclusion is evidence for it. It's not really crucial to my point. Anyway, in attempting ot defeat the instantial model, philosopher Nelson Goodman came up with two problems. They both revolve around ravens being black.
The first is pretty straightforward: All ravens are black. Any black raven we see, by the instantial model, works to help prove that. Over time these build up and we're pretty sure All ravens are black. Fairly straightforward. Then Goodman tries to defeat the instantial model with this neat logic trick which I heartily dislike but find fascinating: The counterpositive to all ravens are black is that all non-black things are non-ravens. These are seen as being logically equivalent to one another. But by the instantial model, then, any non-black thing which is also a non-raven is suppot for "all non-black things are non-ravens" and is logically equivalent to supporting the statement "all ravens are black." Which is to say, green leaves are thereby evidence that ravens are black. This is problematic! Now I have a slight quibble here because although the counterpositive is logically equivalent, I have issues with this relationship. It seems to me like evidence supporting the counterpositive shouldn't necessarily count as evidence in support of the original statement, but I've never taken logic (yeah, really) so I can't say why. Anyway, this isn't the point of this blog post.
Goodman's second point is really complicated. My beloved Professor Paul Davies (If you're one of those professors that creepily has a google news alert whenever someone blogs your name and thereby checks student blogs for references, Hi!) prefaced this by saying, "If you're at the bar and you really want to impress someone, tell them about this." Would that he had explained this last class, because I spent a better part of last night trying to impress girls at the bar. I'm way off topic.
Right. Goodman's second point: Let's make a fictitious category called Raveswans. We'll define them as: things which were ravens up until today, and things which today and onward are swans. They have the quality that up until today, they were black, and from today onward, they are white. Hence the statement, All Raveswans are Blight. Now, if we assume that this as a natural category existed, then any black ravens we saw in the past would be evidence for the statement. Which is fine. But the problem is that the statement includes information about the whiteness of swans. Ergo, any black ravens in the past, through this statement, are evidence that swans are white. We've got a major problem!
Now Professor Davies and most of my class didn't find this terribly interesting or important, I don't think, and most of their critiques seemed to rest on the problem that Raveswans aren't a natural category. There's no substantial mechanism linking them, so who cares? It's not really a relevant point to our lives. But here's where I went off on a brain-tangent and spent most of the rest of the class pondering: what if Raveswans were a natural category? Wouldn't it then be a real challenge to instantial induction?
So I had to find a natural category that could illustrate this. I began by thinking about this massive change from ravens to swans within the logic. Is there something in psychology, a field I know much better, that fits the model where something changes before and after a certain date? Then I remembered: Both anecdotally and on surveys, people noted that after 9/11, New Yorkers became MUCH nicer to each other. This is especially with respect to racial tensions (though I imagine Arabs or Muslims in general were left out of these data.) This was, for some reason, big news in the social psych world. In my opinion, it meshes perfectly with the results of the Robbers Cave Experiment and are thusly Not That Interesting, but whatever. So before 9/11, New Yorkers = assholes. After 9/11, New Yorkers = nice. I think you know where I'm going with this.
So I went up to Professor Davies after class and explained to him my reformulation with the statement, "All pre/post-9/11 New Yorkers are Niceholes." He laughed a lot and said it was really clever, which coming from him means quite a lot, as he's certainly one of the smartest people I've ever met.
He thought it over, and seemed to think that the catestrophic nature of 9/11 had something to do with why the scenarios weren't exactly logically equivalent. The Raveswans example, he said, works within nature, which is in general not subject to major changes. I have problems with this response, because I think that a) I think catastrophes happen in nature frequently enough that the same-old-same-old argument doesn't really hold much water and b) because that still has the underlying assumption from above that "The world will continue to be as it has been." Actually, come to think of it, a) and b) are pretty much the same problem. Anyway, Prof Davies said he'd think it over over the weekend and get back to me. But I think he was really impressed, which I don't think I've managed to do just yet. It's probably because I invented the word 'niceholes' and he truly appreciates the use of profanity in philosophy.
Anyway, here's a diagram from my notes from class today modified to include the niceholes. Let me know what you think the flaws in my logic are.
