THE PRINCIPLE OF ECONOMY IN EVOLUTION. 327 



carrying on war, a statesman conducting affairs of government, a 

 merchant engaged in business negotiations, alike take tlie path 

 which, having regard to the whole of the circumstances, offers 

 the least amount of resistance to the attainment of the ends in 

 view. 



All inorganic and organic movements are therefore alike in 

 the fact that each is due to a greatest stress, and takes place in 

 the direction of a least resistance. It is true, of course, that a 

 pedestrian does not rebound, like the billiard ball, from the re- 

 sistances which he encounters in trying to find the easiest path 

 through a forest or over the mountains ; yet he consciously seeks 

 the path of least resistance, and does so because he is diverted 

 into it by the greater resistances of all other paths ; these greater 

 resistances become part of the greatest stress which determines 

 the form of his movement, just as the reactive stress of the cush- 

 ions forms part of the greatest stress that determines the path of 

 the billiard ball. Inorganic and organic movements differ from 

 each other simply in the fact that by living animals the path of 

 least resistance is more or less consciously chosen, while in the 

 inorganic world the path of least resistance is not chosen. And 

 this unlikeness arises out of a more fundamental unlikeness still, 

 from the fact that movement in the realm of the organic has end 

 for its concomitant, though not necessarily conscious end, while 

 in the motion of things inanimate end is wholly absent. Organic 

 movements, that is to say, are all directed to some end, while in 

 the realm of the inorganic, movements are simply unintelligent 

 effects, results, or products of differential stress. In the form of 

 organic movement, end plays a most important part, while in in- 

 organic movement it has no part at all. Thus a pedestrian may 

 find a circuitous route through a forest the easiest if his only end 

 be to pass through it as quickly as possible ; yet, should botaniz- 

 ing be his object, the form of his movement will be quite differ- 

 ent, and may very well be the direction of greatest resistance, so 

 far as physical obstacles to movement are concerned. In the case, 

 moreover, of particular ends, numerous opportunities for the ex- 

 ercise of choice present themselves. The more direct path up a 

 mountain is chosen in preference to the one less direct, yet, when 

 the " easier " path is the more dangerous, the traveler takes the 

 safer and more difiicult passage. So the more efficient tool is pre- 

 ferred to the less perfect instrument ; and so, out of numberless 

 ways in which the ends of life are to be reached, men instinc- 

 tively and consciously choose those which, by encountering the 

 least possible resistances, involve the minimum expenditure of 

 effort. In the case of organic movements, economy of energy is 

 possible because of the presence of end, the existence of various 

 ways of reaching it, and the possibility of choosing the one which 



