PSYCHOLOGY Ixxxvii 



Condillac. But he is careful to say that though every idea 

 is derived from a sensation, not every sensation yields an 

 idea. It is only when attention is fixed upon the sensation, 

 at the moment when it is experienced, that an idea of more or 

 less permanence remains. 



On this theory of physically-existing ideas Lamarck bases 

 his whole theory of intellect. When the nervous fluid 

 traverses the outlines of an idea in the cortex, it is thrown 

 once more into the same type of agitation as when 

 it first engraved that idea. This agitation, being con- 

 veyed back to the nucleus of sensations, gives rise to a 

 fainter repetition of the original sensation : thus we have 

 memory. 



When the nervous fluid passes over several graven ideas 

 at the same time, each portion of the fluid is agitated in a 

 mode corresponding to the idea traversed. When these 

 different streams of fluid, each with its special agitation or 

 mode of motion, reach the nucleus at the same moment, 

 their motions are compounded so as to form a " complex " 

 idea, which is then laid down in the cortex separately from 

 its constituents. Complex ideas may be further combined, 

 and thus Lamarck endeavours to give a physical interpreta- 

 tion of comparison and reasoning. Dreaming is accounted 

 for as an aberrant or haphazard wandering of the nervous 

 fluid, owing to failure of control by the " inner feeling." 

 Dehrium and syncope are similarly explained. But it is 

 needless to enter into further detail on Lamarck's psychology, 

 or to follow out all his apphcations of the general principles 

 cited above. 



§ 9. Conclusion. 



It is an unhappy but necessary characteristic of social 

 evolution that those great leaders of thought and action, 

 who at one time exercise profound influence over their 

 generation, are apt to be unduly criticised by those of 

 a succeeding generation. The works of great men are 



