PREFACE. 



sophy which, building on a few material facts, presumes 

 to assert that it has compassed the bounds of existence, 

 while it nevertheless ignores the most unquestionable 

 phenomena of the human mind and feelings. 



I have to thank my colleague, Professor Barker, for 

 carefully revising several of the sheets most abounding in 

 mathematical considerations. It is approximately certain 

 that in freely employing illustrations drawn from many 

 different sciences, I have frequently fallen into errors of 

 detail. In this respect I must throw myself upon the 

 indulgence of the reader, who will bear in mind, as I hope, 

 that the scientific facts are generally mentioned purely for 

 the purpose of illustration, so that inaccuracies of detail 

 will not in the majority of cases affect the truth of the 

 general principles illustrated. 



December I5th, 1873. 





