224 A STUDY IN HEREDITY 



and, therefore, even more as regards his mental characters than as 

 regards his physical characters, the adult differs from the infant in 

 that which is acquired, not in that which is inborn. At birth the 

 infant's mind is a blank ; he can co-ordinate only a very few 

 groups of muscles {e.g. the breathing, sucking, and defaecating 

 groups), and in the co-ordination is never very delicate and 

 elaborate. He knows nothing of his environment ; he cannot, 

 as can the dragon-fly, instinctively adapt himself to it. But 

 gradually, as his body develops under the influence of use and 

 exercise, his mind develops also under the influences of experience, 

 and the blank left by the retrogression of instinct is filled, and 

 more than filled, by acquired knowledge and ways of thinking 

 and acting. Slowly and painfully the infant learns to co-ordinate 

 his different groups of muscles till at length he can perform such 

 complex acts as speaking, writing, and walking, in which the 

 co-ordination is exceedingly delicate and elaborate. Much, very 

 much, besides the power of co-ordinating his muscles is acquired 

 by man. For instance, all the vast contents of his memory, and 

 all that arises out of memory are, of course, acquired. Here, 

 again, all that is inborn is the power of acquiring the contents of 

 the memory. I have elsewhere defined reason as "the faculty 

 which is concerned in the conscious adaptation of means to ends 

 by virtue of acquired non-inherited knowledge and ways of think- 

 ing and acting." Compare, for instance, the construction of a 

 cocoon by a caterpillar, or the first web-spinning of a spider, with 

 the construction of a house, or the weaving of a net by a man. 

 In the absolute absence of experience the caterpillar and the 

 spider plainly act by virtue of inborn knowledge, and ways of 

 thinking and acting, in other words, by instinct ; the man, on the 

 other hand, as plainly acts by virtue of acquired knowledge and 

 ways of thinking and acting, in other words, by reason. In fact, 

 so vast a part does the acquired factor play in all that is mental 

 in man, that I have been unable to discover any action in him 

 which is purely instinctive. Purely reflex actions he has in 

 plenty, as, for instance, the movements of the various hollow 

 viscera ; but of the few instincts which survive in him (e.g. 



