XXXIV.] 



MENTAL GKOWTH. 89 



I will nuw Slim up the whole of the parallel I have Summary, 

 been endeavouring to draw between organic and mental 

 life and growth. 



The organism grows by means of new material brought 

 from without in the food. So the mind grows by means 

 of impressions brought from without by the senses. But 

 food could not of itself build up an organism. Tlie or- 

 ganism is built up out of the materials of the food, by 

 the action of the intelligent organizing principle of life. 

 So the impressions received by the mind from the senses 

 could not of themselves form a mind. They are organized 

 into knowledge, and become part of the mental structure 

 by the action of the intelligent principle of mental life. 



It is necessary to organic Hfe and growth not only to be 

 constantly acquiring new material, but also to be con- 

 stantly parting with old material So it is necessary to 

 mental life and growth to be not only always acquiring 

 and retaining new impressions, but always also forgetting. 



Organic growth is due to the excess of material acquired 

 over material parted with. So mental growth is due to 

 the excess of what is remembered over what is forgotten. 



In infancy, when the body is growing most rapidly, it 

 is also most rapidly undergoing waste and parting with 

 material. So in childhood, when the mind is acquiring 

 knowledge the most rapidly, it is also forgetting the most. 



The same law of forgetting, and the necessity of for- Forma- 

 getting, are true of a different though closely related set il°^[°^ of 

 of mental phenomena. I mean the process by which action by 



tllG SclTTlB 



habits of action are formed. " We learn to do a thing by law. 

 doing it." The process of learning a mechanical art is 

 this : that actions are at first performed vohmtarily and 

 with conscious attention ; but, in virtue of the law of 



once. But this is an acquired power. Partly through mere habit, partly 

 through voluntary exertion, the student of a language acquires a power of 

 forming the association between a word and its meaning with peculiar 

 facility. I think that children begin to acquire this power while they are 

 learning to speak. But it is not likely that a trace of it exists at the time 

 when language is nothing to the child but sound ; and yet every one's 

 ■ knowledge of language has to begin from that point. 



