68 



HABIT AND INTELLIGENCE. 



[CHAF. 



and the more necessary they are to each other's life. As 

 stated in the chapter on the Direction of Development,^ the 

 more complete is the physiological division of labour, the 

 more complete is also the physiological centralization. It 

 is the same with the mental functions. Consciousness, 

 thought, and will are all distinct, but they are all necessary 

 to each other's development. Thought derives all its 

 materials from consciousness, and furnishes consciousness 

 with the materials of aU the higher emotions. Will is 

 directed by thought, and is nearly always accompanied by 

 consciousness. WiU has also the power of directing 

 thought ; this power is what makes possible that process 

 of thought called abstraction, on which the immeasurable 

 superiority of the reasoning power of man to that of all 

 animals appears to depend. These various relations of 

 interaction between the various mental functions are not 

 less real, and for a complete psychology not less necessary 

 to understand, than their relations of development ; but it 

 is only the relations of development that I shall make any 

 attempt to state in tabular form. 



Develop- 

 ment of 

 thought, 

 feeling, 

 and •\vill. 



Consen- 

 sual and 



I now proceed to state in some detail how I conceive the 

 various mental functions to be derived by development the 

 one from the other. 



We have seen that the germ of all mind is sensation. 

 Tliose mental functions which do not necessarily determine 

 any other actions, but have their end in themselves, that 

 is to say the functions of thought and feeling, have their 

 germ in sensation determining consciousness. The volun- 

 tary powers, on the contrary, have their germ in sensation 

 determining motor action; that is to say, in consensual 

 action. Or we may say, using a different but not a con- 

 tradictory metaphor, and stating another aspect of the 

 subject, that thought and feeling have their roots in the 

 sensory functions of the organism ; and will, or the volun- 

 tary powers, in its motor functions. 



It is impossible to draw the line where consensual action 

 ends and voluntary action begins. I shall use the word 



1 Chapter XII. 



