PREFACE. 



can only be reached by new arguments' 

 and by new methods of proof. 



Many of the questions which are in-' 

 volved in the reasoning of this Essay, 

 are questions which touch upon the pro- 

 foundest problems of our nature and of 

 our history : — On the connection, seem- 

 ingly inseparable, between all mental 

 phenomena and physical organization ; on 

 the truthfulness of any system of classifi- 

 cation which does not take equal cogni- 

 zance of both; on the distinction between 

 intellectual powers and moral character; 

 on the distinction, again, between the 

 mere results of accumulated knowledge, 

 and the working of the original facul- 



