INTRODUCTION. 1 1 



activities going on around him he came to regard 

 the forces of nature as manifestations of some 

 supernatural beings. This was eminently natural. 

 He had a direct consciousness of his own power 

 to act, and it was natural for him to assume that 

 the activities going on around him were caused 

 by similar powers on the part of some being like 

 himself, only superior to him. Thus he came to 

 fill the unseen universe with gods controlling the 

 forces of nature. The wind was the breath of 

 one god, and the lightning a bolt thrown from 

 the hands of another. 



With advancing thought the ideas of polythe- 

 ism later gave place to the nobler conception of 

 monotheism. But for a long time yet the same 

 ideas of the supernatural, as related to the 

 natural, retained their place in man's philosophy. 

 Those phenomena which he thought he could 

 understand were looked upon as natural, while 

 those which he could not understand were looked 

 upon as supernatural, and as produced by the 

 direct personal activity of some divine agency. 

 As the centuries passed, and man's power of ob- 

 servation became keener and his thinking more 

 logical, many of the hitherto mysterious pheno- 

 mena became intelligible and subject to simple 

 explanations. As fast as this occurred these 

 phenomena were unconsciously taken from the 

 realm of the supernatural and placed among 

 natural phenomena which could be explained by 

 natural laws. Among the first mysteries to be 

 thus comprehended by natural law were those of 

 astronomy. The complicated and yet harmonious 

 motions of the heavenly bodies had hitherto been 



