You're right, my statement was far too strong, and I hereby retract it. Instead, I claim that philosophy which is not firmly grounded in the real world such that it effectively becomes another discipline is worthless. A philosophy book is unlikely to contain very much of value, but a cognitive science book which touches on ideas from philosophy is more valuable than one which doesn't. The problem is that most philosophy is just attempts to argue for things that sound nice, logically, with not a care for their actual value. Philosophy is not entirely worthless, since it forms the backbone of rationality, but the problem is the useful parts are almost all settled questions (and the ones that aren't are effectively the grounds of science, not abstract discussion). We already know how to form beliefs that work in the real world, justified by the fact that they work in the real world.. We already know how to get to the most basic form of rationality from whence we can then use the tools recursively to improve them. We know how to integrate new science into our belief structure. The major thing which has traditionally been a philosophical question which we still don't have an answer to, namely morality, is fundamentally reduced to an empirical question: what do humans in fact value? We already know that morality as we generally imagine it is a fundamentally a flawed concept, since there are no moral laws which bind us from the outside, but just the fact that we value some things that aren't just us and our tribe. The field is effectively empty of useful open questions (the justification of priors is one of the few relevant ones remaining, but it's also one which doesn't help us in real life much).
Basically, whether philosophers dispute something is essentially un-correlated to whether there is a clear answer on it or not. If you want to know truth, don't talk to a philosopher. If you pick your beliefs based on strength of human arguments, you're going to believe whatever the most persuasive person believes, and there's only weak evidence that that should correlate with truth. Sure, philosophy feeds into rationality and cog-sci and mathematics, but if you want to figure out which parts do so in a useful way, go study those fields. The problem with philosophy as a field is not the questions it asks but the way it answers them; there is no force that drives philosophers to accept correct arguments that they don't like, so they all believe whatever they want to believe (and everyone says that's ok). I mean, anti-reductionism? Epiphenomenalism? This stuff is maybe a little better than religious nonsense, but it still deserves to be laughed at, not taken as a serious opponent. My problem is not the fundamentals of the field, but the way it exists in the real world.
If you judge philosophy by what helps us in the empirical world, this is mostly correct. The importance of rationality to philosophy (granted the existence of an empirical world) I also agree with. However, some people want to know the true answers to these questions, useful or not. For that, argument is all we've got.
I would mostly agree with rationality training for philosophers, except in that there is something both circular and silly about using empirical data to influence, if indirectly, discussions on if the empirical world exists.
I have naturally read the material here, but am still not sure how to act on two questions.
1: I've been arguing out the question of Foundationalism v.s Coherentism v.s other similiarly basic methods of justifying knowledge (e.g. infinitism, pragmatism). The discussion left off with two problems for Foundationalism.
a: The Evil Demon argument, particularly the problem of memory. When following any piece of reason, an Evil Demon could theoretically fool my reason into thinking that it had reasoned correctly when it hadn't, or fool my memory into thinking I'd reasoned properly before with reasoning I'd never done. Since a Foundationalist either is a weak Foundationalist (and runs into severe problems) or must discard all but self-evident and incorrigible assumptions (of which memory is not one), I'm stuffed.
(Then again, it has been argued, if a Coherentist were decieved by an evil demon they could be decieved into thinking data coheres when it doesn't. Since their belief rests upon the assumption that their beliefs cohere, should they not discard if they can't know if it coheres or not? The seems to cohere formulation has it's own problem)
b: Even if that's discarded, there is still the problem of how Strong Foundationalist beliefs are justified within a Strong Foundationalist system. Strong Foundationalism is neither self-evident nor incorrigible, after all.
I know myself well enough to know I have an unusually strong (even for a non-rationalist) irrational emotive bias in favour of Foundationalism, and even I begin to suspect I've lost the argument (though some people arguing on my side would disagree). Just to confirm, though- have I lost? What should I do now, either way?
2: What to say on the question of skepticism (on which so far I've technically said nothing)? If I remember correctly Elizier has spoken of philosophy as how to act in the world, but I'm arguing with somebody who maintains as an axiom that the purpose of Philosophy is to find truth, whether useful or useless, in whatever area is under discussion.
3: Finally, how do I speak intelligently on the Contextualist v.s Invariantist problem? I can see in basic that it is an empirical problem and therefore not part of abstract philosophy, but that isn't the same thing as having an answer. It would be good to know where to look up enough neuroscience to at least make an intelligent contribution to the discussion.