Abstract

In this dissertation I argue that in the Metaphysics Aristotle successfully defends the principle of non-contradiction against challengers, provided that there are essences or kinds. Aristotle intends the principle to apply to any of the things called being. This includes substances, accidents, essences, motions, and propositions. His defense does not aim at convincing the challenger of the truth of the PNC, for the dedicated opponent cannot be convinced. His defense aims to refute the challenger, i.e. to deduce the truth of the PNC from the challenger's denial. ;Since any attempt to refute the challenger presupposes the truth of the PNC, it seems that the defense begs the question. Aristotle escapes this fallacy, for refutation does not require modifying the challenger's beliefs. ;R. M. Dancy and G. I. Mavrodes believe that Aristotle's defense rests on the claim that believing the truth of the PNC is a necessary condition for believing that a person's words have meaning. Aristotle has no need of such a false claim for his defense to succeed. He bases his defense on the claim that the truth of the PNC is necessary for a person's uttering a significant term that is used to signify. However, Aristotle's defense fails to show that the PNC is necessary for a person's uttering any meaningful term. In order to prove this latter claim the defense must be extended beyond what he provides in the text. This can be done by using the results of Aristotle's defense as a premise for further argument. ;According to Aristotle, the truth of the PNC is necessary for a person's uttering a significant term, because signifying something requires either direct or indirect reference to some essence or kind. Since any essence or kind is necessarily what it is and not anything else, reference to some essence or kind entails the truth of the PNC. Aristotle suggests that singulars or nonessential features can indirectly refer to some essence or kind. However, the defense fails, if it turns out that there are no essences or kinds to which such reference can be made