INTRODUCTION 



consciousness produced in us by unknown ex- 

 ternal agencies." So far, the fundamental pro- 

 positions of Spencer's theory of knowledge are 

 closely followed. The exposition shows, how- 

 ever, both great freedom of expression and de- 

 cided condensation. 



9. Fiske's chapter ii., on the " Scope of 

 Philosophy," corresponds, in its place in the 

 exposition, to Spencer's chapter i. of Part II. of 

 the " First Principles." But the freedom of ex- 

 pository treatment is still greater than before. 

 Spencer's chapter is here briefer than Fiske's. 

 The greater extent of the latter's exposition is 

 due to the fact that he develops at some length 

 the contrast between philosophy and special 

 science, using material drawn from Spencer's 

 essays, as well as illustrations of his own. In 

 chapter iii., on " The Test of Truth," Fiske 

 first appeals, in the early part of the chapter, to 

 Lewes, rather than to Spencer, as his guide to 

 a sketch of the history of the problem of the 

 nature of necessary knowledge. Thereafter he 

 states in his own words Spencer's canon of ne- 

 cessary truth, viz. the principle that " a pro- 

 position of which the negation is inconceivable 

 is necessarily true in relation to human intelli- 

 gence." In illustrating this principle, Fiske 

 unites it with the doctrine of the " relativity of 

 knowledge " in a fashion that the last phrase of 

 xlvii 



