The French socialist Benoit Malon never thought socialism was “une affaire d’estomac” but first of all a “morale sociale” leading to an “altruistic area.” This paper studies the different sources of this moral theory, especially its links with utilitarian philosophy, modern sociology and theories of evolution. It shows how this scientific idealism, this “positive metaphysics” proposes to articulate “struggle for life” (and class struggle) and “association for struggle” or “cooperation for life,” in order to identify socialism with the growth of human sociability and of moral – altruistic and sympathetic – sentiments.