Similar confusions appear in Professor Patten's _Theory of Prosperity_, in a number of places.[68] President Hadley's discussion of "Speculation" falls into this confusion, also.[69] Professor Ely's confusion on this point is instanced in his _Outlines of Economics_, 1908 edition, pp. 358-59.[70] Schaeffle, in his _Quintessence of Socialism_,[71] treats utility as if it were demand. With Professor Flux it seems more a deliberate identification than an unconscious confusion, as he recognizes very clearly the complication which differences in wealth bring in, and yet none the less declares, "The measure of the exchange value is, then, the utility which is on the margin of not being realized, or the marginal utility," and "The series of marginal-demand-prices, corresponding to all the varied possible scales of supply, register, in fact, the utility of the marginal supply for each such scale."[72] It is somewhat disheartening, however, to find Professor Marshall, who has pointed out the confusion on the part of Jevons, allowing his marginal notes to speak of "utility and cost" when the body of the text, to which they refer, is discussing demand and supply.[73] And still more disheartening to find Professor Davenport, at the end of his cautiously written volume, marked throughout by the greatest clearness of thought, and by especially painstaking care in the criticism of this confusion in the writings of others, saying:-- Limitation upon the supply of goods relatively to the need gives value. Thus value in producible goods is ultimately explained by human desires over against a limitation of supply due either to the shortage of instrumental goods or to the irksomeness of effort, or to both. With great esteem for good singing, and with the rarity of good singers, the high gains of prima donnas find sufficient explanation. This, as a separate, unqualified proposition in the "Summary of Doctrine,"[74] is hardly to be counted anything but a _lapsus_, even though recognition is later accorded to the necessity of backing up "utility" with "purchasing power." But it cannot be too strongly insisted, in the first place, that only particular ratios, market relations, can come out of the individualistic analysis of satisfactions of consumption and dissatisfactions of production, and that, in the second place, these ratios, and this relativity, are but surface explanations, that point to, and are based upon, something underlying and definite--without which they would be hanging in the air.[75] FOOTNOTES: [61] See Jevons, _Theory of Pol. Econ._, 3d ed., pp. 88-90; 95-96. [62] See, especially, Pareto, _op. cit._, vol. I, pp. 36-37.