One of the implications of the dynamic perspective is the shift from the traditional individualistic and ‘algorithmic’ theory of scientific rationality to a theory of collective rationality. Such a theory needs to specify who, exactly, is the rational agent of science. From SSR on, Kuhn stresses the importance of the scientific community and, by doing so, he can be credited with the development of an earlier form of social epistemology. At the same time, it is important to point out that he contemplated the existence of scientific communities of different levels of generality. This, in turn, may shed some new light on his history-based model of science. I conclude this chapter by discussing the relation between the history-oriented philosophy of science and the sociological approach to the study of scientific groups.