38 
POLITICAL ECONOMY 
The utilities of certain things are closely 
dependent upon the supplies that we possess 
of other things, and as the supplies of these 
other things become more abundant the 
value of the first things might appreciate or 
depreciate. Consequently we must not affirm 
that to any individual so much of a given 
article means so much utility quite regardless 
of the degree and nature of his opulence. 
Finally it must be remarked that the 
generalisation known as the law of diminish 
ing utility is commonly understood to apply 
to the second case considered above and to 
allege that, income being constant, additional 
supplies of one article add to satisfaction at 
a diminishing rate. 
It is very necessary that the distinction 
implied above between total utility and 
marginal utility should be made explicit. 
With reference to income, total utility is the 
sum of satisfaction which we derive from our 
aggregate outlay, while marginal utility is 
the addition made to total utility by the 
addition of another unit of income, say, by 
supplementing income to the extent of a 
shilling or a sovereign. Any unit of income 
that we please may be taken, provided that 
we make it very small in relation to the sum 
total of income. With reference to particular