vi PREFACE 



significance when treated as parts of the whole to which 

 they belong. This is my excuse for combining a general 

 design with a partial execution. 



Even as to that portion of the hypothesis which I have 

 described as being tested in the present work I cannot 

 pretend that the test is in any sense final. The hypothesis, 

 though it appears to me to stand the test thus far, remains 

 a hypothesis. The nature and limits of animal intelli- 

 gence in its higher forms are matters of keen controversy, 

 and will long remain so. In a science so little advanced 

 as Comparative Psychology the justification for publishing 

 any opinions or arguments must lie not in any pretence 

 to finality, but in the hope of suggesting further 

 investigation. 



The general conception of mental evolution presented 

 in this volume was formed some fourteen or fifteen years 

 ago when I had come into close contact with the criticisms 

 then current on Comte, Mill, and Spencer. The con- 

 ception has been in my mind ever since, subject to 

 constant modification as it was confronted with fresh 

 facts or the better psychological analysis of other thinkers. 

 The general view of evolution which most closely cor- 

 responds to it, is to be found, I think, in Dr. Lester 

 Ward's Outlines of Sociology , published in 1898. I 

 mention these points as indicating the general character 

 of my obligations to other writers. 



My more special obligations in the present work are, 

 first, to Principal Lloyd Morgan and Professor Alexander, 

 who have read the manuscript, and made numerous valu- 

 able suggestions. I hasten to add that they must not be 

 held responsible for anything that appears in the text. 

 In the preparation of my material I was helped by 

 Mr. A. E. Taylor, some of whose work done originally 

 in this connection will, I hope, see the light in another 



