Abstract

This study shows that Aristotle’s introduction of the concept of substance represents a caesura in the history of ontology. The study takes two values for substance into consideration, which are a) substance as an organism (as a biological entity) and b) substance as essence, nature, form of an organism. Substances as organisms are biological concretized properties. Substance as form is the soul directing the organism and the development of the organism; the soul is both the principle of life of the organism and the program which is realized in the organism. The substance as an organism is assigned the central position in Aristotle’s ontology: the organism is not reduced to forces or factors which should have an ontological primacy over the organism; the principle of life and activity of every organism is put into the biological entity and it is not identified with factors that lie outside the organism.