[195] The validity of a theory is not proved if _some_ tendency can be shown to be in keeping with it. The tendency must be _effective_. When the forces that oppose a tendency are relatively great, or the mere obstacles in its way relatively immovable, the tendency cannot be assigned the rank of a force or be laid down as an economic law, not even a static law. True, the difference between an effective and an inoperative tendency is only one of degree. This makes it difficult to decide upon the claims of a proposed law in the particular case, but this is a difficulty which cannot be avoided. The weaker the tendencies taken cognizance of in a given static theory, the more idealistic or refined is that theory. And, at least after a certain point is reached, the more refined the theory becomes, in this sense, the less its degree of validity. To illustrate this, we need but to refer to the present question of skilled labor. Throughout the classical economics runs the idea that the superior remuneration of skill really rewards the extra disutility necessarily undergone in acquiring the skill. Now, if the movement of men among occupations were calculated solely with reference to this disutility, and were free enough, the actual wage of skilled labor could be said to be adjusted to the disutility of the occupation, including the past disutility of acquiring the skill. The extra part of the wage would be a sort of interest on disutility already expended, as suggested expressly by Adam Smith and by Senior. But we need not pursue this idea into its minor complications. The point desired to be made is that the tendency for actual wages of skilled labor to adjust themselves to the disutility of the skilled labor is so submerged (permit a questionable metaphor) beneath other forces, that it makes a theory over-refined to recognize it as a law. I believe it possible to justify nearly all the older theories of value by making a static state to order for each writer, that is, by making one over-refined enough. Put in other words, so far as the older economists were not guilty of self-inconsistencies, their theories could be justified by granting them sufficient _assumptions_. The latter is what we refuse to do. An example of a legitimate static law is that wages tend to equal the specific value-product of labor, as contrasted with the theory that wages tend to adjust themselves to the disutility _of the task_ performed. [196] “On Some Neglected British Economists,” _Economic Journal_, v. xiii, pp. 357-363. [197] _Ibid._, p. 527. [198] See _ante_, pp. 44-5. [199] Adam Smith nevertheless retains the “labor-command” measure of value as applicable to the conditions of advanced society, for criticism of which see _ante_, pp. 30 and 39.