208 THE LESSON OF EVOLUTION 



psychologists, and the principal points involved are 

 well known. But these writers have generally 

 ignored the ancient problem of free-will, although 

 it is of the greatest importance to us in forming our 

 opinion on natural philosophy. To discuss this 

 question satisfactorily it is necessary to review, in 

 however cursory a manner, the main features of 

 mental development. And this is the only excuse 

 I can give for my temerity in touching a subject on 

 which I feel my ignorance. But I trust that I may 

 be able to throw, from the biological side, a little 

 light on this very confused heap of opinion. 



The origin of mental variations. Every man is 

 endowed at birth with a set of mental characteris- 

 tics, or instincts, which we call his personality. As 

 he gets older his personality gradually alters, through 

 the influence of the new ideas which he acquires. 

 The simple ideas which arise from sensations de- 

 rived from the outside, are the chief cause of these 

 changes. The sensations, or perceptions, excite the 

 mind through the medium of motives, or feelings, 

 and thus different mental states, or emotions, are 

 brought about. The principal motives are : (1) 

 Self-preservation ; which consists of the two feelings 

 hunger and fear. The former gives rise to industry 

 and pugnacity ; the latter to prudence and deceit- 

 fulness. (2) Pleasure ; which divides into two 

 branches : Sensuality, or the gratification of the 

 bodily appetites ; and amusement, by which we try 

 to appease the activity of the brain without giving 

 ourselves too much trouble. (3) Sympathy ; from 

 which spring affection, generosity, benevolence, 



