very evident that "psychological," as well as other "natural" motives or causes which remain unchanged throughout the history of mankind, could not be the cause, nor offer any explanation, of the phenomena of capitalist production and distribution which are not common to all human society, but are strictly limited in time as well as in place to only a small portion thereof. It is the same thing that we have already observed in discussing the Materialistic Conception of History:—a constant factor cannot possibly be the cause of a change in the result of an operation.
It is not true, however, that Marx did not adopt the course of examining the actual experiences of exchange relation. Nor is it true that the course he did adopt was that of purely logical deduction. Marx did make a thorough examination of the actual happenings and "experiences" of the exchange relation as Böhm-Bawerk would have him do, although this job did not prove so very "simple" as Böhm-Bawerk imagined it would. In order, however, that he might learn something that was worth while from the actual "experiences" of the exchange relation, he had to put these "relations" to a very careful analysis. In doing that he was certainly guilty of using some very sharp and pure logical reasoning. In this he could not help himself, as he was "naturally" so constituted that to whatever task he applied himself he could not help but use his logic. And that was of the very purest sort. There were, however, no purely logical constructions or abstractions used by him in order to prove his theory of value or surplus value. Those abstractions which he did make, and they will be duly noted, one by one, in the course of the discussion, were not only justified, but required and demanded by the subject matter itself. But he did not start out with any purely logical notions or abstractions, nor did he proceed to any purely logical constructions. On the contrary, he kept to his base all the time, and that was the solid ground of the facts of capitalistic production and exchange. It is very significant that in the whole volume of
