Everyone seems to recognize that the war launched against the United States on Sept. 11 is something new. Unlike past conflicts, there is no identifiable enemy army, no state to bombard or invade, no territory to conquer, no clear objective the attainment of which would allow us to force surrender and declare victory. In truth, we have no idea what our enemy hopes to accomplish. That is because this strange and awful conflict isn't ideological, as the Cold War was, or religious, as the brush-ups in Northern Ireland are, or ethnic, as the wars in Bosnia and Kosovo were. This may be the very first war to be fought over epistemology. As such, it may be terrifyingly intractable. Epistemology is the branch of science and philosophy that concerns knowledge, specifically, how we know what we know. --