Substance and Essence: The Constitution of Quidditas from the Composition of Matter and Form in Thomas Aquinas

Abstract

The purpose of this article is to reconstruct the ontological structure concerning the substance of being in the thought of Thomas Aquinas. It is about the relation between form and matter from the perspective of essence and existence. The main issue is to define the concept of essence that determines the particular being and the essence of common nature. In both cases this essence is called quidditas. In the present article, I present a number of arguments in favour of Aquinas’ principle of individuation. The latter is the designated matter for each being and the designated form for essence itself. Form and matter always depend on each other. The same is also true of essence and existence. In addition, a significant part of the article focuses on the way Aquinas connects the essence of the being with mind and substance. The salient point of the article is the definition of the singularity or multiplicity of essence. Finally, it attempts to show how the substance of prime matter is related to the unity of human mind.