Summary The paper deals with the interrelations among philosophy, sociology, and historiography of science in Thomas Kuhn's theory of scientific development. First, historiography of science provides the basis for both philosophy and sociology of science in the sense that the fundamental questions of both disciplines depend on the principles of the form of historiography employed. Second, the fusion of sociology and philosophy of science, as advocated by Kuhn, is discussed. This fusion consists essentially in a replacement of methodological rules by (...) cognitive values that influence the decisions of scientific communities. As a consequence, the question of the rationality of theory choice arises, both with respect to the actual decisions and to the possible justification of cognitive values and their change. (shrink)