INTRODUCTION. 7 



fortunately, a considerable gap in our knowledge; for these 

 different branches of science stand yet, side by side, uncon- 

 nected, whilst they should, by combination, assist each other. 



This is first shown by the relation of Physiology to Psycho- 

 logy. Both these sciences are usually so limited that the first 

 treats of physical, and the second of psychical life ; hence, the 

 reciprocal actions of the physical and psychical organization 

 remain unexplained, for an investigation of this subject fits 

 neither in the frame of physiology nor of psychology. And 

 yet, as regards the question of the nature of man, the modes 

 and peculiar form of this reciprocal action are of the greatest 

 importance. The obscurity as regards the essence of the soul, 

 and its connexion with the body, is not a sufficient excuse. 

 The disputed points might, without any great loss, remain 

 untouched, if the task proposed were merely to investigate the 

 amount of the influences of the physical organization, with its 

 peculiarities and periodical changes, upon psychical life ; and 

 the kind of reaction the body experiences from psychical 

 activity; to what extent they take place, and what are the 

 proximate and remote results. 



Still larger than the gap subsisting between physiology and 

 psychology, is that obtaining between the physical and histo- 

 rical parts of our knowledge. The History of Civilization is 

 unquestionably developed by the collective action of four 

 connected groups of causes. The first is the physical or- 

 ganization of man. The second presents itself in the form 

 of the psychical life peculiar to each people, which appears 

 developed in all individuals belonging to it in a world agitated 

 by various interests, views, and feelings. Surrounding nature 

 forms the third. The fourth is the sum total of social relations 

 and connexions of individuals and circles of society, inter- 

 nally and externally. The History of Civilization by itself has 

 only for its object the representation, to the fullest extent, of the 

 origin and the decline of each civilization, and the ascertain- 

 ment of their causes. Here it becomes evident how uncon- 

 nected the physical part of the science of man stands beside the 

 historical part ; for we are as yet very far from being able, by 

 a philosophy of history growing out of physiology and psycho- 



