Further, the value concept has been called upon to explain the motivation of the economic activity of society, and value has been conceived of as a motivating force.[148] Schaeffle, especially, has stressed this phase of the matter in his criticism of the socialistic theories of value. "Utility value," he holds, does direct industry into proper channels, but a value based on labor-time would get supply and needs into a hopeless discrepancy.[149] No ratio "between objective articles" will serve these functions which the economists have put upon the value concept. Value as a purely individual phenomenon, varying from man to man, will in no way[150] serve these purposes of the economists. Value as a mere brute quantity of physical objects given in exchange for other physical objects, could in no way serve these purposes. Value must be an objective quality, a _power_, embodied in the object, independent of the individual judgment or desire. A strong feeling that this is so is manifested in the term which the English School so often uses as the equivalent of value, namely, "purchasing power"[151]--a term which Boehm-Bawerk approves.[152] The notion of relativity which has, historically, been bound up with this term, we have criticized in chapter II, and it is not necessary to repeat the argument here. But the other aspect of it, its recognition of the dynamic character of value, and of the quantitative character of value, even though often confusedly and vaguely, seems very much to strengthen the case for the thesis I am maintaining.[153]