This article examines the role of philosophy in the development of the kinetic theory of gases. Two opposing accounts of this role, by Peter Clark and John Nyhof, are discussed and criticized. Contrary to both accounts, it is argued that philosophical views of scientists can fundamentally influence the results of their scientific work. This claim is supported by a detailed analysis of the philosophical views of Maxwell and Boltzmann, and of their work on the kinetic theory, especially concerning the so-called (...) specific heat anomaly. It leads to the conclusion that the scientific development of the kinetic theory cannot be understood without taking into account the role of philosophy. (shrink)