[23] See p. 113.
[24] The disappearance, and the method of disappearance, of such elements of differential utility and disutility occupies a very important place in all marginal-utility ("final-utility") theories of market value, or "objective value."
[25] "Only the simplest and cheapest things that are sold in the market at all bring just what they are worth to the buyers." Page 113.
[26] It is, e.g., open to serious question whether Mr. Clark's curves of final productivity (pp. 139, 148), showing a declining output per unit in response to an increase of one of the complementary agents of production, will fit the common run of industry in case the output be counted by weight and tale. In many cases they will, no doubt; in many other cases they will not. But this is no criticism of the curves in question, since they do not, or at least should not, purport to represent the product in such terms, but in terms of utility.
[27] To resort to an approximation after the manner of Malthus, if the supply of goods be supposed to increase by arithmetical progression, their final utility may be said concomitantly to decrease by geometrical progression.
[28] Cf. Essentials, chap. iii, especially pp. 40-41.
[29] The current marginal-utility diagrams are not of much use in this connection, because the angle of the tangent with the axis of ordinates, at any point, is largely a matter of the draftsman's taste. The abscissa and the ordinate do not measure commensurable units. The units on the abscissa are units of frequency, while those on the ordinate are units of amplitude; and the greater or less segment of line allowed per unit on either axis is a matter of independently arbitrary choice. Yet the proposition in the text remains true,—as true as hedonistic propositions commonly are. The magnitude of the angle of the tangent with the axis of ordinates decides whether the total (hedonistic) productivity at a given point in the curve increases or decreases with a (mechanical) increase of the productive agent,—no student at all familiar with marginal-utility arguments will question that patent fact. But the angle of the tangent depends on the fancy of the draftsman,—no one possessed of the elemental mathematical notions will question that equally patent fact.
[30] A similar line of argument has been followed up by Mr. Clark for capital and interest, in a different connection. See Essentials, pp. 340-345, 356.
[31] Cf. Essentials, pp. 83-90, 118-120.
[32] Cf. chap. xxii, especially pp. 378-392.