PREFACE. XI 



The book is divided into five parts the first contain- 

 ing a general view of the subject; the second, general 

 conditions of scientific research ; the third, personal pre- 

 paration for research ; the fourth, actual working in the 

 art ; and the fifth, various special methods of discovery, 

 classified, and illustrated by numerous examples. I have 

 endeavoured to make the book as interesting to non- 

 scientific persons as the nature of the subject will admit. 

 I have also inserted remarks and suggestions which will 

 probably assist young investigators in disciplining their 

 minds for the avoidance of error, although those remarks 

 may not always bear directly upon the principal object of 

 the book. 



As there is no subject so fruitful of strife as the dis- 

 cussion of theological hypotheses, I have avoided as much 

 as possible all reference to the bearings of original scien- 

 tific inquiry upon religious opinions. There are, however, 

 various truths which apply both to scientific and religious 

 views, and these I have inserted as illustrations of state- 

 ments in science. As, also, various scientific men who 

 have asserted that the actions of the human mind are 

 dependent upon law have had such assertions treated with 

 disbelief and hostility, I have adduced some of the evidence 

 already existing in proof of such statements. 1 I have also 

 shown that even the chief rules of morality are based upon 

 the great fundamental principles of science, especially 

 upon that of causation ; 2 and I hope that other thinkers 

 will develop this great truth and show its correctness 



1 See pp. 127-133. 2 See page 521. 



