Ohne Satz vom Widerspruch keine Entität – Der Satz vom Widerspruch als Strukturformel der Realität

This paper deals with the strategy of defence that Aristotle dedicates to the principle of contradiction; the analysis is concentrated on passages of Metaphysics Gamma 4. The main thesis of the paper is that Aristotle’s strategy is an ontological, and therefore not only a logical, one: the principle is defended on the basis of the, from an ontological point of view, unacceptable consequences which would arise in case of the absence of the principle itself. These consequences are, for instance, the disappearance of properties, of essences, of individual entities and of the plurality of essentially distinguishable entities, since the contents of the properties, the role of properties as essences and the constitution of the individual entities cannot hold, if the principle of contradiction does not hold. The principle of contradiction is, therefore, not only a logical principle: it is the ontological presupposition of the whole reality; without it there is no entity.