The essay “Physique de croyant” is an important statement of Pierre Duhem's position on the relation between his science and his religion. Duhem trod a difficult path, some might say an impossible one, in Republican France because he was both a physicist and a devout Catholic. In this essay, using “Physique de croyant” as a touchstone, I explore the way in which he tried to reconcile his conflicting allegiances. There are several strands in Duhem's strategy that need to be teased out. First, Duhem sought to defend his science against the charge that it was materialist and atheist. He did this with his claim, usually called the autonomy thesis, that physics and metaphysics are fundamentally different enterprises—that physics, properly conducted, has no metaphysical implications and requires no metaphysical support. This did not deny metaphysics its rightful territory. Second, Duhem used his segregationist position to defend the Roman Catholic Church against the assaults of the positivist scientism then in favor with the Republicans. Third, he also sought to protect his science against fellow Catholics who wanted to use it for polemical purposes. I develop and evaluate these lines of defense.