MENTAL EXISTENCE IN THOMAS AQUINAS AND AVICENNA
Black, Deborah L.
Mediaeval Studies, Vol. 61 (1999)
Traditionally it was the case that in philosophical circles, when the name of Thomas Aquinas was raised, the doctrine that would most readily come to mind was the distinction between essence and existence, and the related claim that the act of existence (esse) rather than Aristotelian form is, in the oft-cited words of the Disputed Questions on the Power of God, ― the act of all acts and ―the perfection of all perfections. Thomism more often than not meant ―existential Thomism, and Aquinas‘s interpreters emphasized the centrality of this insight for virtually all aspects of his philosophy.
It was, of course, recognized by existential Thomists—at least the most historically sensitive among them—that the distinction between essence and existence itself, as an addition to the basic Aristotelian metaphysics of form and matter, was not a Thomistic innovation, but primarily one of the many legacies bequeathed to Aquinas by his Islamic predecessor Avicenna (Ibn Sina, 980–1037)