THIS book claims to "call in question not a few of the favourite
doctrines of economists." It's main purpose is to substitute for
Mill's Theory of Value the doctrine that "value depends entirely
upon utility." The rate of exchange of two commodities will,
when the equilibrium has been attained, be such that the utility
to each individual of the last portion of the commodity which
he obtains is only just equal to that of the last portion of the
other commodity which at this rate he gives in exchange for it.
The utility of a commodity is in part "prospective," that is,
dependent on the benefit which will at a future time accrue from
its possession: and this depends partly upon the difficulty that
there might be in obtaining something before that time to supply
its place. Though "labour is often found to determine value,"
it yet does so "only in an indirect manner by varying the
degree of the utility of the commodity through an increase in
the supply." Bearing in mind what has been said about pro-
spective utility, it is almost startling to find that the author
regards the Ricardian theory as maintaining labour to be the
origin of value in a sense inconsistent with this last position.
But the language of Ricardo on this point was loose with system:
and that of many of his more prominent followers differs from
his only in that its looseness is not systematic. By a natural
reaction, attempts have been made by a series of able men to
found the theory of value exclusively upon the neglected truth.

Although the difference between the two sets of theories is of
great importance, it is mainly a difference in form. We may,
for instance, read far into the present book without finding any
important proposition which is new insubstance. But at length
he definitely commits himself: at the end of his Theory of
Exchange we read--

Labour affects supply, and supply affects the degree of utility which
governs value, or the ratio of exchange. But it is easy to go too far in
considering labour as the regulator of value; it is equally to be remembered
that labour is itself of unequal value....I hold labour to be essentially

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