 While developing a science of morals founded on moral doctrine, Durkheim and Lévy-Bruhl were heavily dependent upon this aspect of the System. Like the word ‘sociology’, the word ‘altruism’ was coined by Comte. Being deeply aware of what man and animals have in common, Comte was close to what is known today as ‘evolutionary ethics’: he saw cooperation between men as continuous with phenomena of which biology gives us further examples. The same interest in biology led him to link medicine to moral doctrine and even to religion. In our modern societies, the study of the human being ‘is now irrationally parcelled out amongst three classes of thinkers: the Physicians, who study only the body; the Philosophers, who imagine to study the mind; and the Priests, who specially study the heart’ (1852, v. 2, 437; E., v. 2, 356). To remedy this and to respect the unity of our nature, he proposed giving the new clergy a role in medicine, considering for example that there is no better endorsement of a rule of hygiene than a religious decree. Before dying, he still had the time to outline, in his letters to Audiffrent, the rudiments of a sociological theory of diseases.