What is the “unity of physics” and how far can it be accomplished? Before considering these questions let us look at a wider problem—the unification of all the sciences. This is itself a special case of an even wider question, the unification of all human knowledge, which I cannot dwell on here. The term “unification of the sciences” usually refers to a unification of the results obtained in the sciences; the problem of coordinating the scattered and immense body of specialized findings into a systematic whole is a real one and cannot be neglected. It includes a comparison of the methods and results of cosmology, geology, physics, biology, behavioral science, history and the social sciences in different ages. But first of all it implies a unification of scientific language. Some difficulties in science, even within a specialized discipline, arise because one cannot be sure whether two scientists speak about the same or different problems or whether they state the same or different opinions in their different scientific languages.

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