iv PREFACE. 



ciety, men had been taught to love the pursuit 

 of knowledge and the exercise of reflection, by 

 the imperious calls of newly created wants. 

 This is a very old opinion. People, too, having 

 confounded the causes of excitement existing 

 around us in the world with the various facul- 

 ties of the mind to be excited, have even sup- 

 posed that our propensities, sentiments, and our 

 intellectual and reflecting powers have been de- 

 rived from education ; and that from the con- 

 tingent circumstances of different individuals 

 have arisen the varieties of the human charac- 

 ter; without reflecting on the infinite variety of 

 organization observable in individuals through- 

 out the creation, and without ever perceiving 

 that unless there were conditions in ourselves 

 of the different manifestations of the mind, the 

 objects around us could never excite, nor edu- 

 cation ever improve our several faculties. I 

 have always believed that there were differences 

 in the native structure of persons which inde- 

 pendently of, though perhaps modified by, early 

 habits and associations, have inclined them na- 

 turally to the pursuit of different branches of 

 science. And, I think, the recent investiga- 

 tions of modern physiologists will verify this 

 opinion, and will demonstrate the material con- 



