vi I'REFACE. 



themselves, not only in tlie individual but in its offspring. 

 This law is fundamental in both the unconscious and in the 

 conscious life; or, to use commoner language, it is a funda.- 

 mental law of life and mind. The law of the association of 

 ideas, which is justly regarded as a fundamental law of mind, 

 is only a case of the law of habit. I have made as full a 

 statement as I have been able to do of the laws under which 

 habits form, disappear, alter under altered circumstances, and 

 vary spontaneously. 



The word Intelligence scarcely needs definition, as I use it 

 in its familiar sense. It will not be questioned by any one 

 that intelligence is found in none but living beings ; but it is 

 not so obvious that intelligence is an attribute of aU living 

 beings, and co-extensive with life itself. When I speak of 

 intelligence, however, I mean not only the conscious intelli- 

 gence of the mind, but also the organizing intelligence which 

 adapts the eye for seeing, the ear for hearing, and every other 

 part of an organism for its work. The usual belief is, that the 

 organizing intelligence and the mental intelligence are two 

 distinct intelligences. I have stated the reasons for my belief 

 that they are not distinct, but are two separate manifestations 

 of the same intelligence, which is co-extensive with life, though 

 it is for the most part unconscious, and only becomes fully 

 conscious of itself in the brain of man. 



Habit is in itself obviously an unintelligent principle. 'No 

 intelligence is involved in the mere tendency to repeat an 

 action or to perpetuate a character. But when the laws of 

 Habit and of Intelligence have been stated, the question arises 

 whether intelligence is an ultimate fact, incapable of being 

 resolved into any other, or only a resultant from the laws of 

 habit. This is by far the most important of all questions now 

 under scientific discussion, and perhaps the most important that 

 science can ever have to consider. 



From the point of view adopted in this work, this question 



