CHAPTER V 



THE INHERITANCE OF MENTAL ABILITY 



"We inherit our parents' tempers, our parents' conscientiousness, 

 shyness, and ability, as we inherit their stature, forearm, and span." 

 Karl Pearson. 



WE have seen that feeble-mindedness and other forms of 

 mental defect tend to be strongly transmitted. Can it be shown 

 that the same statement applies to superior ability? For various 

 reasons the doctrine that mental traits are inherited has been 

 regarded with suspicion, and has frequently encountered active 

 opposition. Many writers, influenced by a theological or meta- 

 physical bias, have been reluctant to admit that the laws of 

 heredity which apply to the transmission of physical traits hold 

 also for the mind. Many political and social theorists have found 

 it convenient to minimize the importance of the innate mental 

 differences between men, and have attempted to explain such 

 mental differences as were only too obvious as the result of 

 accidents of education, early experience, and other circumstances 

 external to the individual himself. The doctrine of the equality of 

 man preached by Rousseau and his followers and embodied in our 

 own Declaration of Independence had a tendency to prevent due 

 recognition of the fact that human beings differ profoundly in 

 their inherited mental gifts. The admission of such inheritance 

 might prove a dangerous concession to the claims of aristocracy, 

 and it is not surprising, therefore, to find such a champion of 

 popular rights as Thomas Paine contending against the possi- 

 bility of the inheritance of mental ability. Writers of a much 

 later period, though inspired by much the same motives, have 

 expressed similar views. Henry George, who, like many other 

 socialists, attempted to explain the differences among men as 

 chiefly the production of an iniquitous social order, stated that 



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