Pioneering historians of science from the 19th century accounted for past, natural philosophy. Since the 18th century, historians of philosophy had covered this field as part of a wider narrative of past philosophy. Some early historians of science contrasted the methodologies governing the two historical disciplines, creating the impression that they were mutually independent. Modern commentators have tended to take these declarations at face value. This article argues that Tannery and Duhem, some of the first historians of science, transferred historiographical concepts from history of philosophy to history of science; their uses of the concept system of philosophy is one case in point