In a letter to Engels (24 August 1867), Marx says that the best of his book (Capital) are (i) the “dual character of the labour embodied in commodities” and (ii) the surplus value theory. Marx’s vindication of first point is the subject of the present article.1 We contend that the « dual character of the labour embodied in commodities » is a fundamental and specific property of a commodity society. Marx is right when he calls our attention to it…