  Nevertheless, the emergence in the latter quarter of the twentieth century of serious efforts to provide an evolutionary account of human understanding has potentially radical consequences. The application of selectionist models to the development of human knowledge, for example, creates an immediate tension. Standard traditional accounts of the emergence and growth of scientific knowledge see science as a progressive enterprise which, under the appropriate conditions of rational and free inquiry, generates a body of knowledge which progressively converges on the truth. Selectionist models of biological evolution, on the other hand, are generally construed to be non-progressive or, at most, locally so. Rather than generating convergence, biological evolution produces diversity. Popper’s evolutionary epistemology attempts to embrace both but does so uneasily. Kuhn’s “scientific revolutions” account draws tentatively upon a Darwinian model, but when criticized, Kuhn retreated (cf. Kuhn 1972, pp. 172f with Lakatos and Musgrave 1970, p. 264). Toulmin (1972) is a noteworthy exception. On his account, concepts of rationality are purely “local” and are themselves subject to evolution. This, in turn, seems to entail the need to abandon any sense of “goal directedness” in scientific inquiry. This is a radical consequence which few have embraced. Pursuing an evolutionary approach to epistemology raises fundamental questions about the concepts of knowledge, truth, realism, justification and rationality.