  Duhem made a number of enduring contributions to thermodynamics and physical chemistry. Among these were the Duhem–Margules and Gibbs–Duhem equations, which deal with reversible processes in thermodynamics as quasi-static limiting processes and give a general proof of the Gibbs phase rule. These results were obtained in the context of a program of generalized thermodynamics called “energetics.” Indeed, Duhem’s entire scientific program was driven by the conviction that a generalized thermodynamics should be foundational for physical theory, thinking that all of chemistry and physics, including mechanics, electricity and magnetism, should be derivable from thermodynamic first principles. Duhem started from the concept of the thermodynamic potential (the topic of his failed thesis), deploying it in a manner similar to that of potentials in mechanics, so as to represent all physical and chemical changes. The program finds its mature statement in his Traité d’énergétique of 1911; it was well received by late-nineteenth-century energeticists, such as Wilhelm Ostwald and Georg Helm. So important was energetics for Duhem, that his work in the history and philosophy of science has been viewed as an attempt to defend its aims and methods (see Lowinger 1941). More recently, Niall Martin and others have argued for the importance of religious motives in Duhem’s work (see Martin 1991, Jaki 1991) and it has become clear in the course of Duhem’s writings that he expected the endpoint of science to harmonize with the teachings of the Catholic Church.