42 ESSAYS OF A BIOLOGIST 



of purposed for unpurposed progress is itself a step in 

 progress. 



As another corollary of our concept of progress, it 

 follows that we can and should consider, not only the 

 direction of any evolutionary process, but also its rate. 



An evolutionary process, if it is to be considered 

 progressive, must have a component in one particular 

 direction — a, direction which we have already defined. 

 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 herbivore, pursuer 

 and pursued, led during the development 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 advance ; 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 perhaps 

 to resolve various difficulties of ethics — how, for 



