Darwin’s views on the Descent of Man 151 
must read his life and the introduction to The Descent of Man. From 
the moment that he was convinced of the truth of the principle of 
descent—that is to say, from his thirtieth year, in 1838—he recognised 
clearly that man could not be excluded from its range. He recognised 
as a logical necessity the important conclusion that “man is the co- 
descendant with other species of some ancient, lower, and extinct 
form.” For many years he gathered notes and arguments in support 
of this thesis, and for the purpose of showing the probable line’ of 
man’s ancestry. But in the first edition of The Origin of Species 
(1859) he restricted himself to the single line, that by this work 
“light would be thrown on the origin of man and his history.” In 
the fifty years that have elapsed since that time the science of the 
origin and nature of man has made astonishing progress, and we are 
now fairly agreed in a monistic conception of nature that regards the 
whole universe, including man, as a wonderful unity, governed by 
unalterable and eternal laws. In my philosophical book Die 
Weltrdtsel (1899)) and in the supplementary volume Die Lebens- 
wunder (1904)?, I have endeavoured to show that this pure 
monism is securely established, and that the admission of the all- 
powerful rule of the same principle of evolution throughout the 
universe compels us to formulate a single supreme law—the all-em- 
bracing “Law of Substance,” or the united laws of the constancy of 
matter and the conservation of energy. We should never have 
reached this supreme general conception if Charles Darwin—a “mo- 
nistic philosopher” in the true sense of the word—had not prepared 
the way by his theory of descent by natural selection, and crowned 
the great work of his life by the association of this theory with a 
naturalistic anthropology. 
1 The Riddle of the Universe, London, 1900. 
2 The Wonders of Life, London, 1904. 
