in the theory of value and prices. 23 



§14. 



Utility as defined in the preceding sections does not involve the 

 etconomist in controversy as to the laws of the subjective states of 

 pleasure and pain, the influence of their anticipation as connected 

 with their probabilities,* the vexed questions whether they differ in 

 quality as well as in intensity and duration, f whether duty can or 

 cannot exist as a motive independently of pleasure,]; etc. 



It does not follow that these discussions have no meaning or im- 

 portance. Doubtless pleasure and pain are connected with desire 

 and doubtless they have an important biological and sociological 

 function as registering "healthful" or "pathological" conditions.§ 

 But the economist need not envelop his own science in the hazes of 

 ethics, psychology, biology and metaphysics. 



Perhaps utility is an unfortunate word to express the magnitude 

 intended. Desirability! would be less misleading, and its opposite, 

 undesirability is certainly preferable to dis-utility. " Utility " is the 

 heritage of Bentham and his theory of pleasures and pains. For us 

 his loord is the more acceptable, the less it is entangled with his 

 theory. 



§ 15- 



This chapter may be thus summarized: 

 Postulate : Each individual acts as he desires. 



Definitions of utility, 



(2) and (1) ut. of A ^ ut. of B 



if the given indiv. at the given time 



prefers A to B or neither. 

 . ut. of dA 



if ut. of c?A=z:ut. of oidK (M total) 

 and ut. of dl^z=z\\t. of c?M (M also total). 



(4) . -Y\ = Marginal utility. 



c?U 



(5) yr- = Unit of utility (util.) (A being given). 



* Jevons, p. 72. f Jevons, p. 28, etc. 



X Darwin, Descent Man, I, p. 76, Sidgwick, Methods Ethics, Ch. IV. 

 § Marshall, Prin. of Econ., p. 181, Spencer, Data of Ethics, p. 79, L. Stephen, 

 Science of Ethics, p. 366. 



II Marshall, Prin. of Econ., p. 306. 



