Seyyed Mohammad Esmail Seyyed Hashemi - Associate Professor, Shahid Beheshti University, Tehran, Iran
Ali Akbar Abdol Abadi - Assistant Professor, Shahid Beheshti University, Tehran, Iran.

Avicenna is an influential philosopher whose contributions in ontology led to the transformation of Greek philosophy into philosophical theology in the Middle Ages. He distinguished between existence and essence, divided beings into necessary and contingent beings, and believed in the objectivity of existence. This article discusses Avicenna’s innovations in philosophical ontology and its influence on Christian ontology and theology, especially on Aquinas’ thought. The article focuses on the distinction between existence and essence and its implications in Avicenna’s philosophy and studies its influence on Aquinas’ theology. It will show that although Aquinas, especially in his De Ente et Essentia, is influenced by Avicenna’s ontology, his understanding of Avicenna’s views are sometimes inaccurate, and this has led him to disagree with Avicenna in some cases.

existence, Essence (Quiddity), Objectivity of Existence, Avicenna, Aquinas