Kant introduces empiricism as a deficient position that is unsuitable for the generation of scientific knowledge. The reason for this is that, according to him, empiricism fails to connect with the world by remaining trapped within the realm of appearances. If we follow Galen’s account of the debate ensuing among Hellenistic doctors in the third century B.C., empiricism presents itself in an entirely different light. It emerges as a position that criticises medical practitioners who stray away from the here and now by indulging in theory-driven a priori forms of reasoning. In so doing empiricism remains at all times committed to the world and its agents. In this paper Galen’s account of empiricism will serve as a means to unravel the dynamics of a discussion that aims to reassess the standards of a dogmatic scientific practice. By looking at Bacon’s and Gassendi’s perception of the ancient medical tradition, this paper will furthermore show that the understanding of what empiricism is crucially depends on the understanding of what scepticism is.