52 BASIS OF THE PBOBLEM 



Among men, even in the lowest stage in which they have been 

 studied, the position is entirely different. Owing to the develop- 

 ment of conceptual thought men act with some ideal object in 

 view. Customs grow up which in their origin must be traced 

 to some process of reasoning, however obscure, and action 

 deliberately undertaken, as well as custom, may affect the 

 realization of the power of reproduction. Thus among the lowest 

 of primitive races we find that men abstain from intercourse for 

 various motives which we must regard as due to the presence of 

 reason. Or again, they may practise certain forms of mutilation 

 of the sexual organs which may affect the power of reproduction. 

 The origin of such a custom may be hidden ; it may be almost 

 certain that it was not originated with any understanding of its 

 effect upon reproduction and even that its effect has never been 

 recognized ; nevertheless originally such a custom could only 

 have arisen if reason was present. Similarly, among the lowest 

 races there are abundant examples of the practices of abortion 

 and infanticide which, though they do not affect fecundity, have 

 an important bearing upon the quantitative aspect of the popula- 

 tion problem and are again the products of reason. 



Among men, therefore, owing to the development of a higher 

 stage of mental power, fecundity is not realized to the full, and 

 we have to distinguish between the power of reproduction, which 

 we have called fecundity, and the actual degree of reproduction, 

 which we shall call fertility. It may, perhaps, assist to emphasize 

 what is meant if for a moment we think of the reproductive 

 process among animals as ' mechanical '. The introduction of 

 this term should not be taken to have any ultimate significance 

 any reference whatever to the true nature of mental process. It 

 is only used as a convenient term to illustrate the difference 

 between reproduction among animals and among men. Among 

 all species in a state of nature reproduction may be thought of 

 as ' mechanical ', whereas reproduction among men is never 

 1 mechanical '. The number of young produced in the case of 

 the human species is far from being completely correlated with 

 the fecundity. There may be all degrees of difference between 

 fecundity and fertility. Among species in a state of nature fecundity 

 and fertility are for all practical purposes one and the same thing 

 because reproduction is ' mechanical ' whatever may be the stage 

 which mental development has reached. Further, such differences 



