256 SCIENCE AND THE HUMAN MIND 



solutions. Yet to the scientific protagonist at each 

 stage, an animating faith in the eternal verity of his 

 own creed, whether of vitalism or mechanicism, is a 

 priceless possession. A man without convictions 

 cannot be convinced. Let him therefore face his 

 facts fairly and choose his line. As long as he does 

 not try to fit his conclusions to any preconceived ideas 

 of what may be good for man to believe, he will play 

 a useful part ; but, " die Philosophic muss sich hiiten 

 erbaulich sein zu wollen." 



Introspective psychology is at least as old as the 



Greeks. Experimental psychology, and comparative 



Modern P s y cno lgy> the study of the minds of 



Psychology, different races of men and animals, are 



among the newest born of the sciences. 



Experimental determinations can now be made of 

 the sharpness of the senses, and the action on them of 

 injury, fatigue and other changes ; of the power of 

 memory and the effect of association of ideas on 

 memory and on action. 



The human mind possesses the special faculty of 

 constructing complex ideas and following trains of 

 thought. Here too association comes into play ; 

 association not only of sense impressions which have 

 followed each other in the past, but also of things 

 similar in various ways but perhaps never before 

 associated. In this formative process of comparison 

 the importance of language becomes manifest. The 

 possibility of giving all similar things a class-name 

 helps the mind to frame a universal or general con- 

 cept of that class. To call all dogs dogs, and not 

 merely Joe, Nelson, Caesar and Smut, is a very real 



