Universalist claims are based on the denial or at least the bracketing of the fact that science is a social product, that it is inscribed in specific cultures. But does cultural relativism automatically lead to epistemological relativism? Against a widespread tendency to infer the latter from the former, this chapter proposes a negative answer to the question. This implies a critique of the traditional conceptions of the history of science as linear and Western. A decentred and transcultural history of science reveals the numerous contacts and circulations of scientific concepts, theories, and methods between cultures, including those called "non-Western". Moreover, the holistic idea of incommensurability between epistemes or paradigms does not mean they are impervious to each other, since any circulation between paradigms implies operations of borrowing, displacement, and reinterpretation. The plurality of paradigms or competing theories neither calls into question the existence of a reality that is external to them, nor the validity of some of them (more than others).