Philosophy is notorious for not answering the questions it tackles. Plato posed most of the central questions more than two millennia ago, and philosophers still haven't come to much consensus about them. Or at least, whenever philosophical questions begin to admit of answers, we start calling them scientific questions. (Astronomy, physics, chemistry, biology, and psychology all began as branches of philosophy.)
A common attitude on Less Wrong is "Too slow! Solve the problem and move on." The free will sequence argues that the free will problem has been solved.
I, for one, am bold enough to claim that some philosophical problems have been solved. Here they are:
- Is there a God? No.
- What's the solution to the mind-body problem? Materialism.
- Do we have free will? We don't have contra-causal free will, but of course we have the ability to deliberate on alternatives and have this deliberation effect the outcome.
- What is knowledge? (How do we overcome Gettier?) What is art? How do we demarcate science from non-science? If you're trying to find simple definitions that match our intuitions about the meaning of these terms in ever case, you're doing it wrong. These concepts were not invented by mathematicians for use in a formal system. They evolved in practical use among millions of humans over hundreds of years. Stipulate a coherent meaning and start using the term to successfully communicate with others.
I think this objection, though I empathize with your bringing it up, is not really worth our time in considering.
Look, we all know, if we are honest, that there is a kind of skepticism (the result of realizing the problem of solipsism and following through on its logical consequences) that cannot be eliminated from the system. It is universal and infects everything.
For this reason, we really need to know more about why these folks have objections to these conclusions. Why we should give particular credence to the opinions of members of the philosophical professions is not obvious, as certainly this site testifies to the fact that you need not be a professor of philosophy to investigate philosophical questions. I suspect, but let us test, that in a fair number of cases the kind of doubts that are raised can be raised in any and every case of a claim of truth. If this is the case, then what matters it? I do not think our interests, practical as they seem largely to be, require that we be constantly limited by such doubts.
I am sure this reveals me as a scientist, but cannot we agree that in the cases of such doubt we should just move on and get on? We should, I think, care about doubts specific to the problems we are considering rather than doubts general to all problems, or we can be pretty sure that we are not going to get anywhere on any topic ever.