Pierre Duhem is the discoverer of the physics of the Middle Ages. The discovery that there existed a physics of the Middle Ages was a surprise primarily for Duhem himself. This discovery completely changed the way he saw the evolution of physics, bringing him to formulate a complex argument for the growth and continuity of scientific knowledge, which I call the ‘Pierre Duhem Thesis’ (not to be confused either with what Roger Ariew called the ‘true Duhem thesis’ as opposed to (...) the Quine-Duhem thesis, which he persuasively argued is not Duhem’s, or with the famous ‘Quine-Duhem Thesis’ itself). The ‘Pierre Duhem Thesis’ consists of five sub-theses (some transcendental in nature, some other causal, factual, or descriptive), which are not independent, as they do not work separately (but only as a system) and do not relate to reality separately (but only simultaneously). The famous and disputed ‘continuity thesis’ is part, as a sub-thesis, from this larger argument. I argue that the ‘Pierre Duhem Thesis’ wraps up all of Duhem’s discoveries in the history of science and as a whole represents his main contribution to the historiography of science. The ‘Pierre Duhem Thesis’ is the central argument of Pierre Duhem's work as historian of science. (shrink)