[Sorry about the length; my brain didn't want to stop. I'll break it up into a couple comments if need be. ]

What if i interpret the above to show that philosophers should not do psychology? Certainly, figuring out the best way to reason has been as important in philosophy (if not more than) figuring out how we actually reason.

Sometimes philosophers screw it up and confuse a normative claim for a descriptive claim. Perhaps (and I am not committed to this as anything more than a possibility) classical Aristotelian categories are not the way we actually represent categories when we're being lazy or care-free, but when we are trying to reason with the highest certainty possible, Aristotelian categories work best.

Is there no natural human category which is truly binary, has sufficient and necessary causes, and is semantic? 'Electron', or 'quark' seem plausibly Aristotelian to my intuition, and are certainly semantic.

On the other hand, we may sometimes run into a target of inquiry which requires that we form concepts for its study, but there are no Aristotelian categories which do the job, due to the nature of the target. In this case, we should definitely use fuzzy logics and the like; but I wouldn't doubt that the closer your fuzzy sets approximate Aristotelian categories, the easier categorical inference becomes.

So, if you are simply claiming that brains do not always use Aristotelian categories, I agree, and think you have provided sufficient evidence for the claim. But this is not so much a hit to philosophers doing logic/philosophy coming from discoveries in cog-sci, as it a hit to philosophers doing cog-sci coming from cog-sci. However, if you would go on to say that we shouldn't treat categories as Aristotelian-lyish as possible in philosophy/logic, I would say that you have not done enough to show this (not to say that LW doesn't elsewhere).

That philosophers arguing about how the brain works (or any other question about what is going on out there) is fruitless, is not something I needed cog-sci to tell me. Philosophers have been warning against philosophizing when we should just go out there and look, for centuries. Those philosophers that involved themselves in classical conceptual analysis in the way you described, did not fail in that they failed to look at cog-sci; they failed in that they couldn't tell that that was not philosophy time, it was go check the world time; this is a much more general and fundamental mistake class than failing to update on a new piece of evidence.

I like philosophy as loosely cog-sci + maths (at least the epistemological/ontological/logic-ish parts). But I would prefer to add to it the normative part of philosophy. Not how do we reason most often (a question at least as psychological as it is philosophical, if not more), but also what is the best, least error prone, fastest, way to reason? (Psychology tells us how we reason/think, but it doesn't know a damn thing about how we should reason/think.) This is not an unassailable field. We could use the tools we develop in Bayes and Calculus to do much of this work deductively. Modern Bayesian epistemology is already moving in this direction. I might also add to philosophy the contrasting and bridging of how we should reason to how we actually do. Of course, this is not to say that that is all philosophy is. Many philosophers have also been interested in forming descriptions of the way things are put together out there, in the most general sense of the terms, e.g., the field of metaphysics. But anyone who is working in ontology, epistemology, and logic, on both the normative and descriptive parts is likely a philosopher.

so to summarize:

How we reason/think is the domain of Psychology/cog-Philosophy/Philosophy of science. How we should reason/think is the domain of logic/epistemology/ontology/Philosophy of science. Getting from how we do reason/think, to how we should reason/think, is the domain of general philosophy/rationalism. Formulating as complete as possible a cohesive, qualitative, general, and abstract description of reality using as divers a range of information as is available, is the domain of metaphysics.

I do admit however that of all of these fields which I think of as essentially intertwined, Psychology is the only one which appears on the list which is not traditionally thought of as philosophical. This motivates me to further investigate philosophy's relationship to psychology.

I am a philosophy major; and I think of myself as a philosopher. But maybe we should just say that philosophy is a dead field; and "philosophy" a hopelessly vague and outdated 2000+ year old term; but many of its tenants, open questions, and methods, survive (normally in some improved form) in the modern field of LW style rationality.

And BTW: I don't see why you can't just say that an item which satisfies some but not all of the necessary conditions for membership in C, is C-ish; the more it has, the C-isher it is; if it has all of them, it is as C-ish as possible, and if it has none it is completely non-C-ish. This seems to capture both the typicality and Aristotelian categorical views as one hypothesis containing both types of categories and inference. Is there anything in cognitive science to suggest that the brain's categories don't function like that? The term you use to refer to some set of necessary conditions need not be the term you use to refer to that set of conditions next week; as long as any category you use consistently follows the rules described above, for as long as it remains consistent. I'm sure someone else has proposed a similar enough idea, anyone know its name?