82 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 4 



almost beyond recognition, increasing in extent, dignity, and beauty, 

 as whole armies of laborers have patiently added wing after wing, 

 story upon story, and pinnacle to pinnacle. Yet the theoretical 

 physicist must admit that his own department looks like nothing so 

 jnuch as a building which has been brought down in ruins by a 

 succession of earthquake shocks. 



The earthquake shocks were, of course, new facts of observation, 

 and the building fell because it was not built on the solid rock of 

 ascertained fact, but on the ever-shifting sands of conjecture and 

 speculation. Indeed it was little more than a museum of models, 

 which had accumulated because the old-fashioned physicist had a 

 passion for trying to liken the ingredients of Nature to familiar 

 objects such as billiard balls, jellies, and spinning tops. While he 

 believed and proclaimed that Nature had existed and gone her way 

 for countless eons before man came to spy on her, he assumed that 

 the latest newcomer on the scene, the mind which could never get 

 outside itself and its own sensations, would find things within its 

 limited experience to explain what had existed from all eternity. 

 It was expecting too much of Nature, as the ruin of our building 

 has shown. She is not so accommodating as this to the limita- 

 tions of the human mind ; her truths can only be made compre- 

 hensible in the form of parables. 



Yet no parable can remain true throughout its whole range to the 

 facts it is trying to explain. Somewhere or other it must be too wide 

 or too narrow, so that " the truth, the whole truth, and nothing but 

 the truth " is not to be conveyed by parables. The fundamental 

 mistake of the old-fashioned physicist was that he failed to distin- 

 guish between the half truths of parables and the literal truth. 



Perhaps his mistake was pardonable, perhaps it was even natural. 

 Modern psychologists make great use of what they describe as " word- 

 association." They shoot a word at you, and ask you to reply im- 

 mediately with the first idea it evokes in your uncontrolled mind. 

 If the psychologist says " wave ", the boy-scout will probably say 

 " flag ", while the sailor may say " sea ", the musician " sound ", the 

 engineer " compression ", and the mathematician " sine " or " cosine ". 

 Now the crux of the situation is that the number of people who will 

 give this last response is very small. Our remote ancestors did not 

 survive in the struggle for existence by pondering over sines and 

 cosines, but by devising ways of killing other animals without being 

 killed themselves. As a consequence, the brains we have inherited 

 from them take more kindly to the concrete facts of everyday life 

 than to abstract concepts; to particulars rather than to universals. 

 Every child, when first it begins to learn algebra, asks in despair 

 " But what are a;, y, and s? " and is satisfied when, and only when, 



