ENGINEERING AND PURE SCIENCE — SWANN 211 



concretely understandable matter in its day — through electrodynamics, 

 he is now more or less content to adapt himself to any new philosophy 

 which fits the facts and he is willing to forego too much desire for 

 understandability in terms of horse sense. 



THE ORIGIN OF PERIODS OF STAGNATION 



Perhaps I may here make a slight digression in relation to the 

 general significance of scientific theories. The matter has a bearing 

 upon that cycle of depression in science in which, every now and 

 again, we seem to come to the conclusion that everything worth while 

 has been done and nothing remains but to cull over the old material. 

 What is the reason for this condition of affairs ? I think the reason 

 is not far to seek. When a new set of phenomena reveal themselves, 

 the man of science seeks to correlate these phenomena in the form of 

 a theory. Sometimes in the formulation of the postulates of the 

 theory there are details which are artificial to him, there are starting 

 points which seem unreal, so the theory is at first abstract and few 

 understand it. To the layman, in fact, some of the postulates of the 

 theory may seem to be nonsense. However, the working purpose of 

 the theory is not primarily to give pictorial satisfaction to the lay 

 mind, but rather to correlate the phenomena which it concerns. The 

 theory is a means by which, through the process of saying few 

 things, we may deduce many as a consequence. Having molded the 

 theory so as to comprehend all the newly discovered phenomena, the 

 theory of itself starts to predict other phenomena; and it is well 

 worth while to look for these phenomena. And so there comes a 

 period in which science devotes itself to verifying the predictions 

 of the theory and tracing its consequences to their limit. In the olden 

 days, this took a long time. In modern times it has taken increas- 

 ingly shorter and shorter periods, as the would-be Ph. D.'s and their 

 mentors stalk around like roaring lions seeking something to measure. 

 In any case, before very long everything that the theory suggests as 

 an object of measurement has been measured and every phenomenon 

 which it has predicted has been found, if it is a good theory. By 

 this time, the theory has acquired a good deal of prestige. It 

 has been responsible for suggesting many new discoveries. Those pos- 

 tulates and premises in the theory which were a little repugnant to us 

 in the beginning have become more natural and reasonable in our 

 eyes. They sit well in the realm peopled by the interesting phenom- 

 ena they have brought into it. They, the nonsense of yesterday, have 

 become the common sense of today. And now, the theory, having 

 grown old in a useful life, becomes rather like a conventional old 

 gentleman who, radical in his youth, has become conservative with 

 age, who now hates to see anything other than what he has been 



