Sec. 5] UTILITY 47

that the total desirability of any group of goods is the sum
of the desirabilities of the successive units. The total
desirability of the ten chairs, for instance, is found by adding
 together (1) the desirability of having only one chair,
(2) the desirability of having a second chair, (3) a third,
(4) a fourth, ete., until ten chairs have been considered.
These successive desirabilities will evidently continually
diminish. Hence their sum, or the total desirability of the
group, is not the same thing as ten times the marginal desirability.
 In this is found the explanation of the fact that
the possessor of the chairs regards them as possessing much
more total desirability to him than the total desirability
of the money which they cost, although the loss of any one
of the ten chairs may not represent more desirability than
the desirability of the money which that one chair cost.
As is well known to all students of the modern theory
of value, marginal desirability lies at the root of the determination
 of value and price. We are lere concerned,
however, not in applying the concept of marginal desirability
 to the determination of economic magnitudes, but
merely in explaining its nature.
Although the definitions which have been given of desirability
 serve to explain its nature, they do not enable
us to employ it in a quantitative manner. The exact
measurement of desirability is a subject of much importance,
 as well as of great difficulty. Inasmuch as in the
present work only an incidental use will be made of these
concepts, it does not seem proper here to enter into these
discussions.
! Cf. Fetter’s Principles of Economics, New York, 1904, pp. 25-26.
? See the writer's “ Mathematical Investigations in the Theory of
Value and Prices,” Transactions of the Connecticut Academy of Arts
and Sciences, 1893, Vol. IX; Pigou, Economic Journal, March, 1903,
Vol. XIII; Pareto, Cours d’Economie Politique, Vol. 1; Giornale
d’Economisti, August, 1892; J. B. Clark, “Ultimate Standard of
Value,” Yale Review, November, 1892; Seligman, Principles of
Eeonomies, Longmans, Green & Co., 1905, Chap. XIII; Chin tao
Chen's Societary Circulation, a doctor’s thesis, Yale Univ., 1906.