Duhem first expounds the holistic thesis, according to which an experimental test always involves several hypotheses, in articles dating from the 1890s. Poincaré's analysis of a recent experiment in optics provides the incentive, but Duhem generalizes this analysis and develops a highly original methodological position. He is led to reject inductivism. I will endeavor to show the crucial role history of science comes to play in the development of Duhem's holism.