SCIENTIFIC METHOD 515 



840. " If, on matters so much the most important with which 

 the human intellect can occupy itself, a more general agreement 

 is ever to exist among thinkers ; if what has been pronounced 

 ( the proper study of mankind ' is not destined to remain the only 

 subject which Philosophy cannot succeed in rescuing from Empiri- 

 cism ; the same process through which the laws of many simpler 

 phenomena have by general acknowledgment been placed beyond 

 dispute must be consciously and deliberately applied to those 

 more difficult inquiries. If there are some subjects on which the 

 results obtained have finally received the unanimous assent of all 

 that have attended to the proof, and others on which mankind 

 have not yet been equally successful ; on which the most sagacious 

 minds have occupied themselves from the earliest date, and have 

 never succeeded in establishing any considerable body of truths, 

 so as to be beyond denial or doubt ; it is by generalizing the 

 methods successfully followed in the former inquiries, and adapting 

 them to the latter, that we may hope to remove this blot on the 

 face of science." 1 



841. To sum up: whether we consider the histories of indi- 

 viduals, or peoples, or sciences, or religions, or peace, or war, or 

 education, or commerce, or invention, or legislation, indeed of 

 almost any field of human endeavour, one truth is seen to stand 

 forth vividly and unmistakably the moment our attention is drawn 

 to it the truth that human progress and success depend, and have 

 ever depended, chiefly on a power acquired through antecedent 

 training, a habit, of thinking skilfully about causes and their 

 effects. Thus only have men, by studying the present, been able 

 with any degree of certainty, to realize the past and anticipate' 

 the future. This kind of thinking is skilful only when it is 

 carefully tested and comprehensive. Beginning with general- 

 izations from experience, it proceeds, therefore, to establish 

 these generalizations and extend the area covered by them by 

 a thorough and relentless appeal to reality. Only those indi- 

 viduals have achieved enduring success that have thought in this 

 way. Only those nations have been great and progressive that 



many other men besides were at work to discover the causal relations that link 

 together the different kinds of plants and animals that have appeared on earth. 

 As we have seen, all Mill wrote was then, and is now, strictly applicable to the 

 whole study of causation in relation to living beings that is, to the whole study 

 of heredity and evolution, and all that it implies. To this day, because of funda- 

 mental differences concerning evidence and method, biological thinkers, however 

 right they may be, can, as a rule, convince only minorities of their fellows. 

 1 Op. cit., vi. i. i. 



