In considering the question of rationality, one could hardly do better than begin with the splendidly helpful paper that Steven Lukes published some fifteen years ago — which assembles many of the most important alternative conceptions in the anthropological and sociological literature but which is nearly entirely wrong about the theoretical constraints on rationality itself;¹ or, turn to the quite opposed but genuinely searching attempt to relativize the question in accord with the influential program of the sociology of knowledge, offered recently by Barry Barnes and David Bloor — which, nevertheless, is utterly preposterous.² Luke's paper errs instructively, because, although it raises the essential issues (which it would be a misfortune to lose a grip on), it draws all the wrong conclusions by a series of non sequiturs. The reason, in part at least, undoubtedly lies with Lukes's strong opposition to all forms of cognitive relativism.³