In the first volume of Das Kapital, published in 1867, Karl Marx asks what sets the value of a commodity. His answer is a quantity of time. Es ist also nur das Quantum gesellschaftlich notwendiger Arbeit oder die zur Herstellung eines Gebrauchswertes gesellschaftlich notwendige Arbeitszeit, welche seine Wertgröße bestimmt. It is only the amount of socially necessary labor, or the labor time socially necessary to produce a useful thing, that determines the size of its value. Marx defines this time precisely. It is the time needed to make a thing under the normal conditions of production, with the average skill and intensity of the society. A slow or clumsy worker does not make his product more valuable.