THE SCIENTIFIC IMAGINATION 267 



are not mutually exclusive, but the lower foreshadow 

 the higrher and are subsumed in it. Aristotle, how- 



O ' 



ever, interpreted the lower by the higher and not 

 vice versa. It is no compliment to the scientific dis- 

 coverer to say that his loftiest intellectual achievement 

 is closely akin to fiction, or is the result of a mere 

 brooding on facts, or is accompanied by emotional 

 excitement, or is the work of blind instinct. 



It will be found that scientific discovery, while 

 predominantly an intellectual process, varies with the 

 nature of the phenomena of the different sciences 

 and the individual mental differences of the discover- 

 ers. As stated at the outset the psychology of scientific 

 discovery must be the subject of prolonged investi- 

 gation, but some data are already available. One great 

 mathematician, Poiucare, attributes his discoveries 

 to intuition. The essential idea comes with a sense 

 of illumination. It is characterized by suddenness, 

 conciseness, and immediate certainty. It may come 

 unheralded, as he is crossing the street, walking on 

 the cliffs, or stepping into a carriage. There may 

 have intervened a considerable period of time free 

 from conscious effort on the special question involved 

 in the discovery. Poincare is inclined to account for 

 these sudden solutions of theoretical difficulties on 

 the assumption of long periods of previous uncon- 

 scious work. 



There are many such records from men of genius. 

 At the moment the inventor obtains the solution of 

 his problem his mind may seem to be least engaged 

 with it. The long-sought-for idea comes like an in- 

 spiration, something freely imparted rather than 

 voluntarily acquired. No mental process is more 



