Born and Pauli, in talking of the style of science, meant its relatively stable features, which characterized a long period of scientific progress. “I do not mean,” wrote Born in 1953, “that there exist (outside mathematics) any unchanging principles, a priori principles in the strict sense of the term. But I think that certain general tendencies of thought exist, which change very slowly and which form definite philosophical periods with their own characteristic ideas in all fields of human activity, including science. In a recent letter to me, Pauli used the expression ‘styles’; styles of thought, not only in art but in science too. In adopting this term, I would assert that style is also a characteristic of physical theory, and it is precisely this fact that gives its principles a certain constancy. They are, as it were, relatively a priori principles in relation to the particular period. If one is familiar with the style of one's time, one can make certain cautious predictions. One can at least reject ideas that are foreign to the style of one's time”.