NATURE OF DARWIN'S THEORY. 27 
of the Doctrine of Descent, no longer as the ingeniously 
designed work of a Creator building up according to a 
definite purpose, but as the necessary consequence of active 
causes, which are inherent in the chemical combination of 
matter itself, and in its physical properties. 
In fact, we can most positively assert, and I shall justify 
this assertion in the course of these pages, that by the Doc- 
trine of Filiation, or Descent, we are enabled for the first time 
to reduce all organic phenomena to a single law, and to dis- 
cover a single active cause for the infinitely intricate 
mechanism of the whole of this rich world of phenomena. 
In this respect, Darwin’s theory stands quite on a level with 
Newton’s Theory of Gravitation ; indeed, it even rises higher 
than Newton’s theory ! 
The grounds of explanation are equally simple in the two 
theories. In explaining this most intricate world of phe- 
nomena, Darwin does not make use of new or hitherto 
unknown properties of matter, nor does he, as one might 
suppose, make use of discoveries of new combinations 
of matter or of new forces of organization; but it is 
simply by extremely ingenious combination, by the syn- 
thetic comprehension, and by the thoughtful compa- 
rison of a number of well-known facts, that Darwin has 
solved the “holy mystery” of the living world of forms. The 
consideration of the interchanging relations which exist 
between two general properties of organisms, viz. Inherit- 
ance and Adaptation, is what has here been of the first 
importance. Merely by considering the relations between 
these two vital actions or physiological functions of organ- 
isms, also further by considering the reciprocal inter-action 
which all animals and plants, living in one and the same 
