Those philosophers who, over the last two decades, have been studying scientific discovery, the history of physics and its themata, research traditions, 'scientific revolutions"and, in general, the temporal aspects of physics, should not be seen, I think, as turning aside from the more rigorous and difficult domain of philosophy itself. Rather, the degree to which physics changes in time and, perhaps especially, its penchant for holding onto and continuing to use outmoded theories, though knowing them to be in contradiction to newer ones, has become an increasingly serious problem for philosophy. Such changes and contradictions seem incompatible with any claims which physics might make to truth, even to the lower-level truths of consistency and of accuracy of the data-base called for by logical positivism. Given the temporal flux which is physics, can one still speak meaningfully about knowledge, through physics, of the empirical world? And if physics gives no truth, can any science do so?