Published online by Cambridge University Press: 28 February 2022
Although doubtlessly aimed at later developments in physics, Einstein's famous remark, if interpreted so as to include classical statistical mechanics, nicely captures the spirit of work on the early quantum theory by men like Bohr and Ehrenfest, who, despite their conviction that the classical theories failed, nevertheless mined their riches to the fullest in the development of the new theory. In this paper I try to exhibit and characterize the patterns of reasoning involved in Ehrenfest's attempts to generalize Planck's early theory of the linear harmonic oscillator, and I then employ the same historical case as a basis for arguing that the reduction of problems to problems is an important phenomenon which cannot be fully understood in terms of the reduction of theories.
An abbreviated version of this paper was presented at the 1974 meetings of the Philosophy of Science Association as part of a symposium (with Robert L. Causey and Lawrence Sklar) on the Unity of Science. I am grateful to Professor Dudley Shapere and to John Chapman for helpful advice and to the writings of Martin Klein on the history of the early quantum theory. None of these persons are responsible for errors or inadequacies which remain. I am indebted to the National Science Foundation for research support.