HOW THE MIND GROWS. 289 



that impression revives a whole train or group of previous dis- 

 criminations that are like or related to it ; while the number 

 of those that are called up is the measure of our intelligence 

 regarding it. If something is seen, heard, felt, or tasted, 

 which links itself to no kindred idea, we say " we do not know 

 it ; " if it partially agrees with an idea, or revives a few dis- 

 criminations, we know something about it, and the completer 

 the agreement the more perfect the knowledge. 



As to know a thing is to perceive its differences from other 

 things, and its likeness to other things, it is therefore strictly 

 an act of classing. This is involved in every act of thought, 

 for to recognize a thing is to classify its impression or idea 

 with previous states of feeling. Classification, in all its aspects 

 and applications, is but the putting together of things that are 

 alike the grouping of objects by their resemblances; and as 

 to know a thing is to know that it is this or that, to know 

 what it is like and what it is unlike, we begin to classify as 

 soon as we begin to think. When the child learns to know a 

 tree, for example, he discriminates it from objects that differ 

 from it, and identifies it with those that resemble it ; and this 

 is simply to class it as a tree. When he becomes more intelli- 

 gent regarding it when, for instance, he sees that it is an elm 

 or an apple-tree he simply perceives a larger number of char- 

 acters of likeness and difference. 



How our degrees of knowledge resolve themselves into 

 successive classifications has been well illustrated by Herbert 

 Spencer. He says: "The same object may, according as the 

 distance or the degree of light permits, be identified as a 

 particular negro; or, more generally, as a negro; or, more 

 generally still, as a man ; or, yet more generally, as some liv- 

 ing creature ; or most generally, as a solid body ; in each of 

 which cases the implication is, that the present impression is 

 like a certain order of past impressions." 



In early infancy, when the mind is first making the ac- 

 quaintance of outward things, mental growth consists essen- 

 tially in the production of new ideas by repetition of sensa- 

 tions, although such ideas never arise singly, but are always 

 linked together in their origin. But, when a stock of ideas 



