126 ETHICAL ASPECTS OF EVOLUTION 



impediment. The process itself and its factors are within 

 the bounds of experience, and form a proper subject of 

 philosophical inquiry. Our real difficulty is to determine 

 exactly what we mean by pleasure. For our present pur 

 pose we may disregard the question of what that is, and 

 explain it as the result or the concomitant of the satisfaction 

 of a need, meaning by need any vital process, from eating 

 and drinking to the solution of quaternions. From this 

 point of view it may be regarded as a premium on activity 

 of all kinds. But it occurs in the higher forms of life only. 

 We are unable to attribute pleasure to the winds and the 

 waves, and if we do so to the lower forms of life it is mainly 

 in obedience to supposed philosophical necessities, and not 

 because we observe in them, or can directly infer, the ex 

 istence of anything which nearly resembles the feelings of 

 humanity. For its full manifestation it requires a highly 

 developed consciousness, and its intensity varies with that 

 development. It forms, therefore, a stimulant to activity, 

 that is to say, to the output of energy, which is peculiar to 

 living organisms, and which increases in power with the 

 rise in the scale of evolution. That this is the true function 

 of pleasure there is, I think, little reason to doubt. It 

 operates as a premium on, and does actually stimulate, 

 the output of energy in individual organisms, especially in 

 the higher grades of evolution, and thereby promotes the 

 accumulation of power. But, as it impartially stimulates 

 action of all kinds, good and bad alike, it is unfit to serve 

 as an ethical criterion between conflicting lines of conduct. 

 It is never an end in itself, and it is valuable only in so far 

 as it promotes the process of forward evolution. 



The action of pain is repressive, and its function (or 

 practical effect regarded as a purpose) is to control the 

 output of energy, and preserve it from excess or irregu 

 larity. It discharges within the organism the same kind 

 of office as is performed by natural selection, when that cuts 

 off excessive variation from an established type. It is as 

 necessary an element in the process of evolution as pleasure 

 is ; where one is, the other must be found also, and the 





