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.
A pattern in philosophy is that once a problem is solved, it often seems obvious and trivial in retrospect. Never the less, here are some much-less-controversial solved problems (from http://www.philosophyetc.net/2008/02/examples-of-solved-philosophy.html)
Knowledge does not require certainty. But nor does justified true belief suffice.
Psychological egoism is false: it is possible to act from non-selfish desires, i.e. for some good other than your own welfare.
Rational egoism is false: we are not rationally required to always and only act in our own self-interest.
(E.g. Moral) Principles may take situational variables into account without thereby sacrificing their claim to objectivity.
The question whether God actually exists is independent of the question whether there is genuine normativity ("ought"-ness).
Valuing tolerance needn't lead one to moral relativism. (Quite the opposite.)
Red herrings may (and black ravens may not) constitute evidence that all ravens are black.
It's not analytic (true by definition) that cats are animals. But it is metaphysically necessary: there is no possible world containing a cat that is not an animal.
Slightly more controversial:
"Common-sense" morality, with its agent-relative ends, is self-defeating.
Capitalism is not intrinsically just. (Libertarianism must be defended on consequentialist grounds, if any. Those who think otherwise are confused about the nature of property and coercion.)
It is possible for desires (or ultimate ends) to be irrational. So there is more to rationality than just instrumental rationality.
One may be harmed by events that took place prior to their coming into existence.
Thanks for posting my list! Looking back, I think the third "more controversial" one (about the irrationality of some ultimate desires, e.g. Future Tuesday Indifference) probably doesn't belong on the list. I do think it is very interesting and probably true, but that's a different matter.