Pierre Duhem’s (1861-1916) lifelong opposition to 19th century atomic theories of matter traditionally has been attributed to his conventionalist and/or positivist philosophy of science. Relatively recently, the traditional view has been challenged by the new claim that Duhem’s opposition to atomism was due to the precarious state of atomic theories at the beginning of the 20th century. In this paper, I present some of the difficulties with both the traditional and the new interpretation of Duhem’s opposition to atomism, and provide (...) a new framework in which to understand Duhem's rejection of atomic hypotheses. I argue that although not positivist, instrumentalist, or conventionalist, Duhem’s philosophy of physics was not compatible with belief in unobservable atoms and molecules. The key for understanding Duhem’s resistance to atomism during the final phase of his career is the historicist arguments he presented in support of his ideal of physics. (shrink)