Josiah Gibbs, a theoretical physicist, was born and died in New Haven, Connecticut, and, aside from a few years studying physics in Europe, spent his academic career at Yale. He is one of the few distinguished American theoretical physicists prior to the twentieth century. Gibbs made advances in vector analysis, and he made major contributions to thermodynamics including an insightful diagrammatic method, work on equilibrium and stability, the definition of free energy, and his famous phase rule regarding coexistent phases of a substance. In a vital contribution to thermodynamics Gibbs extended this theory to deal with the rules that describe how chemical interactions are to be integrated with the other thermodynamic processes. He is the inventor of the notion of chemical potential, the key concept of chemical thermodynamics.

For philosophers it is Gibbs's work in statistical mechanics that is of great interest. This work...