HUMAN MENTAL ACQUIREMENTS 419 



which is capable of storing only a particular and a very limited 

 set of facts. The latter hypothesis seems, at least, improbable. 



690. From birth to adult age our physical development is due 

 mainly to the stimulus of use. After the attainment of manhood 

 almost all growth which is not pathological or a mere storing of 

 spare nutriment as fat, is due to that cause. The growth thus made 

 during youth is enormous, but it occurs only on certain predestined 

 lines and within well-defined limits. By limiting the amount of use 

 to which this or that structure is put we may limit its growth ; by 

 putting the structure to a more than normal amount of use we 

 may increase its size somewhat beyond the ' normal.' But there 

 our power ends. The hand is put to a greater variety of uses than 

 any other organ in the body. Yet, even if we begin with the infant, 

 we can only make it large and coarse, or small and fine. It still 

 remains a hand which closely resembles in size and shape altogether 

 normal hands. It is very different in the case of mind. Consider 

 the millions of ' physical ' dexterities we are capable of learning. 

 These are all really mental. For example, our hands do this or 

 that thing dexterously because our minds have learned to direct 

 them readily and rightly. The ' normal ' dexterity of the penman 

 differs widely from that of the woodcutter, the sailor's from that of 

 the surgeon. Yet any of them may be acquired by the average 

 young individual. But physical dexterities are as nothing com- 

 pared to the rest of our mental acquirements ; they are as nothing 

 compared even to the mental acquirements that are most closely 

 related to them. Thus, the architect's manual skill with ruler and 

 pencil is but a small part of his total mental acquirements as 

 architect, and that again is but a small part of his total mental 

 equipment as a man of the world, his other physical dexterities, his 

 acquired mental attitudes, his knowledge of men and things. The 

 average man is capable of becoming an average architect; or, 

 instead, he may acquire skill in one or more of a thousand other 

 occupations. 



691. Physically most of us could fill the places of most other 

 men ; that is our physical structures are capable of doing the 

 work that their physical structures do. Mentally not one of us 

 is capable of filling the place of any other. I, for example, though 

 as large and strong in body, could not mentally fill the place of a 

 workman with whom I am acquainted. I have not the same skill 

 and mental attitudes which have fitted him into a certain niche, the 

 same prejudices, the same ethics, the same knowledge of his world 

 based on past experience. My religious and political convictions 



