12 INTRODUCTION. 



therefore, as a necessary pre-supposition of all sciences, assume 

 that there is a universal and unchangeable human nature ; un- 

 less we place ourselves upon a purely empirical stand-point, 

 from which ' ' universal" signifies nothing more than a relatively 

 high degree of probability, because at different times and under 

 different circumstances it is acknowledged as true by men of 

 different degrees of civilization. 



The question of the unity of species and the nature of man 

 specially belongs to those branches of knowledge which treat of 

 the intellect. These sciences usually make the abstract ideas 

 on mental life, its signification and connection which they find 

 prevalent among peoples of different degrees of culture, the 

 basis of their deductions. And whence should these sciences 

 take their starting points for logical, psychological, ethical, 

 religious, and 83sthetical considerations, if not from the ideal 

 sphere of the people from which they have proceeded ? The 

 inquirer will certainly, in the reception of these ideas, not pro- 

 ceed without discrimination, but he will compare the history 

 of the development of one people with that of his own people. 

 This leads him finally to draw all mankind into the circle of 

 his investigations, since having once entered the wide field of 

 the history of the development of human conceptions, he can- 

 not avoid the conviction, that a too limited notion of man and 

 his intellectual nature must obstruct many of his scientific 

 views. 



Though it has hitherto not been doubted that the same laws 

 of thought are applicable to all men (which is only rendered 

 certain by the assumption of their specific unity), it has been 

 frequently discussed whether all of them are capable of the 

 same intellectual and moral development, whether conscience 

 speaks to all in the same manner, whether the same religion is 

 adapted to the intellectual and moral conception of all. Who- 

 soever denies both this and the unity of the human species, 

 generally acquires his notion of human nature from the study 

 of the Caucasian race, and places his theoretical views on right, 

 morality, and religion, upon quite a different basis from the 

 disciples of the opposite theory. He obtains thus a code of 

 laws and morals which is only binding for one part of humanity; 



