162 DISCOVERY CH. 



Given the results of observation or experiment, the 

 philosopher endeavours to discover a law or principle 

 connecting them. He guesses at their meaning, and 

 invents a hypothesis which will not only explain what is 

 known, but also suggest consequences which may, or may 

 not, be confirmed by future investigations. Prof. A. 

 Senier relates that von Hofmann used to say to him and 

 other research students working in the Berlin laboratory, 

 " I will listen to any suggested hypothesis, but on one 

 condition that you show me a method by which it 

 can be tested." Without such a condition, the creations 

 of a disordered mind would be as worthy of consideration 

 as the speculations of a scientific genius ; and fertile 

 ideas would be sought not in a laboratory but in an 

 asylum. A hypothesis ought, therefore, to be capable 

 of being verified, even though the means may not be 

 available of applying a crucial test to it at the time ; 

 it ought also to be sufficiently definite to admit of proof 

 or condemnation. 



Imagination as distinguished from fancy is an essential 

 attribute of the scientific mind that makes for progress. 

 " With accurate experiment and observation to work 

 upon," says Tyndall, " imagination becomes the archi- 

 tect of physical theory. Newton's passage from a 

 falling apple to a falling moon was an act of the prepared 

 imagination. Out of the facts of chemistry the con- 

 structive imagination of Dalton formed the atomic 

 theory. Davy was richly endowed with the imaginative 

 faculty, while with Faraday its exercise was incessant, 

 preceding, accompanying and guiding all his experi- 

 ments. His strength and fertility as a discoverer are 

 to be referred in great part to the stimulus of the 

 imagination." Darwin was equal to Faraday in im- 

 aginative power ; he was continually forming theories, 



