There are two further arguments for the propriety of this conception, considered primarily as a question of terminology, to be drawn from usage in the treatment of other terms. The first is drawn from a consideration of the function of the value concept in economic science,[36] and of its relation to the concept of wealth. "The notion of value is to our science what that of energy is to mechanics," says Jevons.[37] It is clear that a mere abstract ratio, which Jevons two pages later declares value to be, cannot serve such a purpose. Abstract ratios are subject-matter for mathematics, not for economics. "Wealth and value differ as substance and attribute," (Senior, quoted with approval by F. A. Walker.[38]) With this view, Marx[39] would concur. "Wealth is that which has value," Professor Laughlin states.[40] Clearly a qualitative attribute, and not a ratio, must be indicated here, even though Professor Laughlin elsewhere in the book defines value as a "ratio between two objective articles."[41] And if we take a definition like that of Professor Seligman, who defines wealth in terms which entirely ignore the ideas of comparison and exchange as consisting of those things which are (1) capable of satisfying desire, (2) external to man, and (3) limited in supply,[42] we find no basis for insisting on relativity, exchange and comparison, as essential to the idea of value, which is the essential and distinguishing characteristic of wealth. The science loses in coherency from this diversity of definition. The second argument is similar. Current economic usage speaks of money as a "measure" of values. Professor Seligman uses the expression in the chapter on money in the book referred to. But the point made by General Walker against this expression, when value is defined as a ratio, is absolutely valid. He says:-- I apprehend that this notion of money serving as a common measure of value is wholly fanciful; indeed, the very phrase seems to represent a misconception. Value is a relation. Relations may be expressed, but not measured. You cannot measure the relation of a mile to a furlong; you express it as 8:1.[43] Only on the basis of a definition of value as a quantity is it proper to speak of a "measure of values."[44] I conclude that the value of a thing is a quantity, and not a ratio. It is a definite magnitude, and not a mere relation. What sort of a quantity remains to be seen. FOOTNOTES: [15] Clark, J. B., "Ultimate Standard of Value," _Yale Review_, 1892. p. 258. [16] _E.g._, _The Philosophy of Wealth_, chap. v. [17] _Economics_, p. 92. See also the article by President Hadley on "Value" in Baldwin's _Dictionary of Philosophy_, etc., and "Misunderstandings about Economic Terms," _Yale Review_, vol. IV, pp. 156-70. The same ideas are expressed in all.