The history of science is usually told in terms of experiments and theories and their interaction. But there is a deeper level to the story – a slow change in the attitudes that define what we take as plausible and implausible in scientific theories. Just as our theories are the product of experience with many experiments, our attitudes are the product of experience with many theories. It is these attitudes that one usually finds at the root of the explanation for the curious delays that often occur in the history of science, as for instance, the interval of 15 years between the theoretical work of Alpher and Herman and the experimental search for the cosmic microwave radiation background. The history of science in general and this conference in particular naturally deal with things that happened, with successful theories and experiments, but I think that the most interesting part of the history of science deals with things that did not happen, or at least not when they might have happened. To understand this sort of history, one must understand the slow changes in the attitudes by which we are governed. But it is not easy. Experimental discoveries are reported in The New York Times, and new theories are at least reported in physics journals, but the change in our attitudes goes on quietly and anonymously, somewhere behind the blackboard.

The rise of the Standard Model was accompanied by profound changes in our attitudes toward symmetries and toward field theory.