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

This paper deals with some aspects of the strategy of defence that Aristotle dedicates to theprinciple of contradiction; the analysis is focussed on a number of passages of the chapterMetaphysica Gamma 4. The main thesis of the paper is that Aristotle’s strategy consists in anontological defence of the principle itself: the principle is being defended on the basis of theunacceptable consequences which would arise for the ontology in case of the absence of theprinciple itself. Among these consequences are, for instance, the disappearance of properties, ofessences, of individual entities and of the plurality of essentially distinguishable entities, sincethe contents of the properties, the role of properties as essences and the constitution of theindividual entities cannot hold good, if the principle of contradiction does not hold good. Theadversary of the principle of contradiction will be thus caught in the dilemma of either acceptingthe validity of the principle of contradiction or refusing the principle and, with it, the realityitself. The principle of contradiction appears to be, therefore, the ontological presupposition ofthe whole reality; it is the principle on which the whole reality depends: it shows itself to be notonly a logic law, but also, and more than this, the ontological presupposition for every kind ofentity: without the principle of contradiction there is no entity. The paper follows Aristotle inhis search for instruments in favour of the defence of the principle of contradiction; theseinstruments are, in the end, elements of the reality itself, such as properties, essences andindividual entities: since the disappearance of properties, of essences and of individual essences,which would arise as a result of the collapse of the principle of contradiction, cannot beaccepted, the principle of contradiction must conserve its validity