Since major Western philosophers considered human knowledge and social values in terms of the natural science of their time, it is appropriate to assess the epistemological implications of the contemporary evolutionary theory colloquially known as 'sociobiology." Recent models of natural selection indicate the need to consider human social life in terms of five distinct areas of analysis: individual development (epigenesis), within-group variation, between-group variation, the hierarchical organization of complex systems, and feedback between systemic levels. In each of these domains, modern 'social biology" has striking implications for traditional philosophic questions. While some positions, like those of the Sophists or of the English Empiricists, are seriously challenged by the findings of modern evolutionary biology, Aristotelian ethics and the dialectical tradition from Plato to Hegel appear to be reinforced to a surprising degree by contemporary biological theories.