skilled labor is established by a social process going on behind the backs of the producers, and appears to them merely customary."
Here Marx is only dealing with the value of commodities, that is of objects produced and exchanged by private producers in a society consisting of private producers producing for their own profit. He is therefore not concerned here with "absolute value" whatever that may be but only with the value which is realised in a given form of society. This value under the given social conditions is shaped and measured by the human labor incorporated in the commodities and this human labor shows itself as the expression of simple human energy. But every piece of work is not merely an expression of simple labor force. Very many labor products require the expenditure of more or less time, money, trouble, and acquired skill or knowledge. Do these kinds of compound labor show at the same period of time the same commodity values as simple labor, are they the expression of merely simple labor force? Evidently not. The product of an hour of compound labor is a commodity of higher, double or three times the value of a product of an hour of simple labor. The value of the product of compound labor can in this comparison be expressed through the measure of simple labor; and this reduction of compound labor is carried on by means of a social progress behind the back of the producer, by means of which can here be established according to the theory of value but not explained.
The thing which Marx states here is a simple fact which happens every day before our eyes in the present capitalistic society.
(After some invective and satire hurled at Duehring Engels proceeds:)
