146 HUMANISM vm 



Variation was indefinite. Darwin, that is, did not 

 facilitate his task by supposing a mass of favourable 

 variations to give Natural Selection a good start ; 

 favourable variations were no commoner than they would 

 have been if they had been drawn at random from an 

 indefinite supply of possible variations of all sorts. 



Similarly, in order to avoid the complicating question 

 whether these variations were not produced by definite 

 causes, and so tended in a definite direction, Darwin said 

 in effect Let us suppose these indefinite variations to 

 be accidental. That is, let us waive the question of where 

 they came from. And in this way he arrived at the 

 assumption of indefinite accidental variation on which 

 his theory proceeded. 



It is clear, then, that this essential assumption of 

 Darwinism was originally methodological, that it was a 

 simplification of the facts assumed for purposes of analysis 

 and easier calculation. This is, of course, an everyday 

 procedure in all the sciences, and if a methodological 

 assumption has been skilfully selected, it does excellent 

 service. Now Darwin s assumption was an exceedingly 

 skilful one : for whether or not it was true that Variation 

 was absolutely indefinite and void of direction, it yet 

 ordinarily seemed sufficiently indefinite to enable the ideal 

 theoretical case to throw a most instructive light upon 

 the actual facts. 



Perhaps the character of the assumption of indefinite 

 variation is best illustrated by a parallel methodological 

 fiction which has also played a great part in history. 

 I refer to the assumption of the economic man in 

 political economy. In order to build up the science of 

 wealth, the early economists disentangled the primary 

 laws of wealth-production by the methodological assump 

 tion of the economic man. They said : Let us consider 

 man as a wealth-producing animal ; let us suppose, 

 therefore, that the production of wealth is his sole object 

 in life. In that case the economic man must be taken 

 as (i) absolutely laborious, as never distracted from his 

 work by emotional indisposition or laziness, as a perfect 



