DEMAND 
45 
ence of income from the one line of expenditure 
to the other, so long as the two marginal 
utilities differed. Hence, I should try to get 
the two marginal satisfactions equal. What is. 
true in this matter of two things is evidently 
true of any number. 
There is a reason for most things, even 
for this law’s profusion of names. Each name 
is appropriate and, in the absence of any 
fixation of terminology by convention, some 
writers have favoured one name and some 
another. The law is called the law of equi 
marginal returns because when it is observed 
equi-marginal returns result. It is called the 
aw of substitution because the end, equi 
marginal returns, is attained by the process, 
of substitution already described. It is called 
the law of indifference because, when it is 
observed, a person’s scheme of expenditure 
is so devised that it is a matter of indifference 
to him whether he spends a minute accession 
of income on any one thing or on any other. 
Before concluding our study of demand and 
expenditure, a few words are needed to indicate 
the extent to which the laws of demand and 
expenditure hold in actual practice. It may 
have been gathered from the exposition above 
that the individual is unceasingly engaged 
in balancing the utilities of different courses