42 ESSAYS OF A BIOLOGIST 



fined. But this is not all; for even if it be moving 

 in the right direction, and yet be moving extremely 

 slowly, it may, if it have any interaction with a much 

 more rapid progressive movement, actually exert a 

 drag on this; its relative motion — relative to the 

 main current of progress — will be backwards, and we 

 may have to class it as the reverse of progressive. 

 For example, the interaction of carnivore and herbi- 

 vore, pursuer and pursued, led during the develop- 

 ment of the vertebrates to the evolution of much that 

 was good — speed, strength, alertness, and acuity of 

 sense — and of many noble types of living things. 

 But with the advent of man, different methods have 

 been introduced, new modes of competition and ad- 

 vance; and the tiger and the wolf not only cease to 

 be agents of progress in its new form, but definitely 

 stand in its way and must be stamped out, or at 

 least reduced to a condition in which they can no 

 longer interfere as active agents in evolution. 



Some such considerations as these will help per- 

 haps to resolve various difficulties of ethics — how, for 

 instance, that which seems good to me may seem evil 

 to another. Even the good, if it be a drag on the 

 better, is evil. Expressed thus, the proposition is a 

 paradox; but expressed in terms of direction and rela- 

 tive speed, it is at once intelligible. 



But the test of any such general biological theory 

 as I have outlined will be its application to human 

 problems. And here too, I venture to say, the value 



