THE KINSHIP OF LIFE. 47 
The theory of evolution, in brief, is this: There ex- 
ists in all things a tendency to become specialized and 
differentiated. In accordance with this tendency nebu- 
lous masses have been concentrated into planets and the 
generalized creatures of early time have been special- 
ized into distinct forms. The formula of the process of 
evolution as stated by Mr. Spencer resolves itself into 
this: “Evolution is a change from an indefinite, inco- 
herent homogeneity to a definite, coherent heterogeneity 
through successive differentiations and integrations,” 
That this is true in the world of life is beyond ques- 
tion, and we have reason to believe that something of 
the sort is true in the world outside of life, whether the 
laws and forces in question be in essential respects com- 
parable or not, 
The influence of the theory of descent on all forms 
of modern mental activity has been great beyond com- 
parison. The thoughts of every student 
have been more or less modified by it. 
In philosophy as in science the publica- 
tion of the Origin of Species has been 
the great event of the nineteenth century. Not only. 
have all the strictly biological sciences undergone a 
complete transformation since the year 1859, but such 
allied sciences as psychology, philology, sociology, and 
ethics have felt the same impulse and have fallen under 
the same influences. Even the organization of charities 
in every well-ordered community is avowedly based on 
the principles of Darwinism. 
The various attacks on the theory of descent have 
been nearly all based on the question of the origin of 
man. For the human race is likewise a 
species of animals, and from its physical 
side it must be discussed with other species. If we sup- 
pose that the various forms of the lower animals and 
5 
Influence of 
theory of 
descent. 
Origin of man. 
