126 THE RELATIONS OF MAN 



I have heard of the announcement of a formula touching 

 " the ordained continuous becoming of organic forms," it 

 is obvious that it is the first duty of a hypothesis to be 

 intelligible, and that a qua-qua-versal proposition of this 

 kind, which may be read backwards, or forwards, or side 

 ways, with exactly the same amount of signification, does 

 not really exist, though it may seem to do so. 



At the present moment, therefore, the question of the 

 relation of man to the lower animals resolves itself, in the 

 end, into the larger question of the tenability or untena- 

 bility of Mr. Darwin's views. But here we enter upon 

 difficult ground, and it behoves us to define our exact po- 

 sition with the greatest care. 



It cannot be doubted, I think, that Mr. Darwin has 

 satisfactorily proved that what he terms selection, or select- 

 ive modification, must occur, and does occur, in nature ; 

 and he has also proved to superfluity that such selection is 

 competent to produce forms as distinct, structurally, as 

 some genera even are. If the animated world presented 

 us with none but structural differences, I should have no 

 hesitation in saying that Mr. Darwin has demonstrated 

 the existence of a true physical cause, amply competent to 

 account for the origin of living species, and of man among 

 the rest. 



But, in addition to their structural distinctions, the 

 species of animals and plants, or at least a great number 

 of them, exhibit physiological characters — what are known 

 as distinct species, structurally, being for the most part 

 either altogether incompetent to breed one with another ; 

 or if they breed, the resulting mule, or hybrid, is unable 

 to perpetuate its race with another hybrid of the same kind. 



A true physical cause is, however, admitted to be such 

 only on one condition — that it shall account for all the 

 phenomena which come within the range of its operation. 



