822 THE STOftY OF THE EARTH AND MAN. 



in nature for evolution, properly limited, as well as for 

 other things, and that the idea of creation by no means 

 exclud.es law and second causes. 



Limiting ourselves in the first place to theories 

 of evolution, and to these as explaining the origin 

 of species of living beings, and especially of man, 

 we naturally first inquire as to the basis on which 

 they are founded. Now no one pretends that they 

 rest on facts actually observed, for no one has ever 

 observed the production of even one species. Nor 

 do they even rest, like the deductions of theoretical 

 geology, on the extension into past time of causes 

 of change now seen to be in action. Their proba- 

 bility depends entirely on their capacity to account 

 hypothetically for certain relations of living creatures 

 to each other, and to the world without; and the 

 strongest point of the arguments of their advocates is 

 the accumulation of cases of such relations supposed 

 to be accounted for. Such being the kind of argu- 

 ment with which we have to deal, we may first 

 inquire what we are required to believe as conditions 

 of the action of evolution, and secondly, to what ex- 

 tent it actually does explain the phenomena. 



In the first place, as evolutionists, we are required 

 to assume certain forces, or materials, or both, with 

 which evolution shall begin. Darwin, in his Origin 

 of Species, went_ao__far as to assume the existence of 

 a few of the simpler types of animals ; but this view, 

 of course, was only a temporary resting-place for his 

 theory. Others assume a primitive protoplasm, or 



