I don't think that anything of any consequence is known a priori: all our knowledge is built up by modifying the lore passed on to us by our ancestors in light of our experiences, and the best a philosopher can do is to learn as much about what has been discovered in various empirical fields, and use it to try to craft an improved synthesis.
Philip KitcherSchopenhauer's thought that Will is insatiable, that once satisfied in one form it must be expressed in new desires, is inherited both by Mann and by Aschenbach (it's in Mahler, as well). So life is inevitably incomplete.
Philip KitcherMy ethical naturalism sees us as facing the predicament of being social animals without evolved adaptations that make social life easy. The fundamental problem that sparks the ethical project lies in our limited responsiveness to one another. The only way we have to address that problem is through a representative, informed, and engaged conversation.
Philip KitcherWhen I try to outline the history of ethical life, it's sometimes possible to find evidence for a hypothesis about how important transitions actually went. Often, however, that isn't so. There are many facts about human life in the Paleolithic we're never likely to know.
Philip Kitcher