Karl Marx rarely wrote about the emancipated society of the future. He was mainly interested in utopias, but detested highly regulatory, highly oppressive, and highly dogmatic interpretations. As Miguel Abensour rightly reminds us, his object was the transformation of utopia into a critical communism. What exactly does this consist of? In Book III of Capital - in the unfinished manuscript, published posthumously by Friedrich Engels in 1894 - we find an important section that has been frequently mentioned but rarely analyzed. [...]