248 PERSONAL PREPARATION FOR RESEARCH. 



research, is the power of detecting essential resemblances 

 and differences, amidst mere apparent likeness or diversity, 

 and associating together intrinsically similar phenomena. 

 A discoverer compares, and then chooses and rejects. It 

 is often by detecting some real similarity between the 

 results we have obtained and some other known pheno- 

 mena, that we are led to assume that they are due to the 

 same cause or causes. An investigator must also possess 

 a keen perception of fallacy in order to detect quickly false 

 hypotheses and explanations. Some investigators are more 

 apt to fail in finding the true explanations of their results, 

 than in discovering new phenomena ; others are better able 

 to discover quantitative relations of known truths than new 

 qualitative facts. No discoverer sees the truth all at once, 

 but has to make numerous guesses, nearly the whole of 

 which are erroneous, before he detects the true one, and in 

 this way the errors of a great man are more numerous than 

 those of a lesser one ; the greater man, however, nips his 

 errors in the bud, whilst the lesser man allows them to 

 flourish. 



Every great investigator makes a great number of 

 hypotheses, but rarely publishes more than a few; Kepler, 

 however, published all his ideas indiscriminately : -' The 

 mystical part of Kepler's opinions, as his belief in astro- 

 logy, his persuasion that the earth was an animal, and 

 many of the loose moral and spiritual as well as sensible 

 analogies by which he represented to himself the powers 

 which he supposed to prevail in the universe, do not appear 

 to have interfered with his discovery, but rather to have 

 stimulated his invention, and animated his exertions. 

 Indeed, where there are clear scientific ideas on one 

 subject in the mind, it does not appear that mysticism 

 on others is at all unfavourable to the successful prosecu- 

 tion of research.' 



