The concept of substance determines the real, i.e. that which exists independently, or the ontological conditions of independence. The author investigates Aristotle's relation of substance and accident, the relation of substance and substance (Descartes) and finally the relation of substance, relation and relation (Leibniz). Without the ontological function of substance, processes of growth, the preservation of the species, the identity of the human being and the formation of social entities could not be understood.