ents
of value are always made specifically, and single units of the supply
of goods are appraised apart from the remainder. The total utility of
atmospheric air is infinite, since the loss of the whole of it would
mean the total destruction of animal life; but the specific utility
and the value of air is _nil_, since no one limited part of the supply
has any practical importance. A roomful of it might be destroyed with
impunity. So the cereal crops of the world, taken as a whole, have
almost infinite importance, since their destruction would result in
universal famine; but each bushel of grain has an importance that is
relatively small. The loss of it would impose no serious hardship upon
the average consumer, since he could easily replace it. The value of
the crop is determined by the importance of one bushel taken
separately and by the number of the bushels. If we estimate the
importance of one unit of the supply of anything, express the result
of the estimate in a number, and then multiply this by the number of
units in the supply, we express the _value_ of this total amount. The
_total utility_ of it, on the other hand, is measured by the benefit
which we get from the supply in its entirety, or by the difference
between the state we are in when we have it all and that to which we
should be reduced if we lost it all and were unable to replace it. To
measure any such total utility we contrast, in imagination, our
condition with the full supply on hand and a condition of total and
hopeless privation, in so far as these goods and similar ones are
concerned.

_This Method of measuring Wealth Universal._--These principles apply
as well to the economy of a solitary islander of the Crusoe type as
they do to that of a civilized society. A Crusoe does not need to
measure values for purposes of exchange, but he has other reasons for
measuring them. It is for his interest to use his own labor
economically, and to that end he should not put too much of it into
one occupation and too little into another. When, by reason of a large
store of wheat on hand, the specific importance of it is small,--or,
if we use a common expression, when the utility of the "final
increment" of it, which a man might secure by making an addition to
his supply, is small,--he should divert his labor to raising goats or
building huts, where the utility of the increment of product to be
gained is, for the time, greater. The solitary man thus well
illustr