 The image of the rise of classical genetics just drawn is reminiscent of Thomas Kuhn’s philosophy of science (Kuhn 1970), or of David Hull’s account of the rise of cladistic taxonomy (Hull 1988). It is a controversial issue whether such an image is compatible with a broadly rational construal of scientific practice. Kuhn thought that there exists no external standard of rationality that we could appeal to in order to answer this question, but he also held that science is the very epitome of rationality (Kuhn 1971, 143f.). According to Kuhn, there is an emergent social rationality inherent in modern science that cannot be construed as the exercise of individual rational faculties. Hull (1988) seems to be taking a similar view.