118 MEXTAL EVOLUTION IN ANIMALS. 



analysis of Ideation. But in connection with Memory it is 

 necessary to touch upon the Association of Ideas, and there- 

 fore I shaU do so now, notwithstanding^ the disadvantao-e 

 which arises from considering the property that ideas pre- 

 sent of becoming associated before we consider the ideas 

 themselves. The truth is that here as elsewhere one labours 

 under a difficulty in dealing with the faculties of Mind in the 

 probable order of their evohition, from the fact that these 

 faculties require to be treated separately, although they have 

 not arisen separately, or in historical sequence. Therefore 

 one has to meet the difficulty by occasionally forestalling in 

 earlier chapters general and well-known principles, the de- 

 tailed consideration of which forms the subject-matter of 

 later chapters. Such a difficulty arises now, and necessitates 

 a somewhat premature treatment of what I may call the 

 elements of ideation. 



Throughout the present work I shall use the word Idea 

 in its widest sense. As few terms have been used with a 

 greater variety of meanings, I think it is better to state here 

 at the outset what I take to be its most general meaning, 

 and therefore the one which, as I have said, I shall always 

 attach to it. 



If after looking at a tree I close my eyes and then arouse 

 a mental picture of what I have just seen, I may say indif- 

 ferently that I remember or imagine the tree, or that I have 

 an idea of it. The idea in this case would be simple or con- 

 crete — the mere memory of a previous sensuous perception. 

 Now between this and the highest product of ideation there 

 is all the interval between the lowest and the highest develop- 

 ment of Mind. The range of meaning over which the term 

 Idea thus extends has seemed to many writers inconveniently 

 large, and they have therefore imposed upon it various limi- 

 tations. But as all such limitations are of a purely artificial 

 kind, I shall nowhere limit the term in itself, but whenever I 

 have occasion to specify one or other class of ideas, I shall do 

 so by employing the convenient adjectives, Concrete, Abstract, 

 and General, in the senses which I shall have to explain 

 further on. Meanwhile it is enough to say that whenever 

 I employ the term Idea alone, I mean it to be a generic 

 term. 



We have already seen, while treating of the obverse or 

 physiological side of ideation (in the chapter on the Physical 



