all. We are now in a position to perceive the true relation between
utility and price. The relation is one which exists not between price
and total utility, but between price and marginal utility. If we know
only that a housewife will buy weekly 5 pounds of sugar at 8 cents per
pound, but 6 pounds at 7 cents, we know nothing of the total utility
of sugar to her. We do not know how much she might be prepared to pay
rather than go without 3 pounds, 2 pounds, or any sugar at all. But we
do know that, when she buys 6 pounds, the marginal utility of sugar is
in her judgment worth something which does not differ greatly from the
price. We can, therefore, say in general terms that the price of a
commodity measures approximately its marginal utility to the
purchaser.

This statement is perfectly consistent with the paradox noted above
that the most useful commodities such as bread, salt and water are
very cheap. For when we say that these commodities are supremely
useful, we mean only that their total utility is very great; that,
rather than do without them altogether, we would offer for them a
large proportion of our means. But we would not value very highly a
small addition to the bread, water or salt that we habitually consume;
nor would most of us feel it as a very serious deprivation if our
consumption of these things were curtailed by a small percentage. In
other words, their _marginal_ utilities are small, and it is only the
_marginal_ utility that has any relation to price.


§4. _The Marginal Purchaser_. A possible objection to the preceding
argument deserves to be considered. Some readers may find the picture
I have drawn of the hesitating housewife entirely unconvincing. They
may declare that her mind does not work at all in the manner I have