IV PREFACE. 



We have, therefore, endeavoured to define our standpoint 

 sharply in the introduction, and to preserve it rigidly 

 throughout the work. This is, indeed, a case in which, 

 as Theodor Fechner has recently said, a definite deci- 

 sion has to be made between two fundamental alter- 

 natives. May our exposition afford a lucid testimony 

 to this dictum of one of the patriarchs of the philo- 

 sophical view of nature. 



Strasburg, October iWi, 1873. 



Oscar Schmidt. 



