“Essentia is a new word, indeed, which was not used in the Latin speech of old, but which has come into use in our own day so that our language should not lack a word for what the Greeks call ousia for this expressed very exactly be essentia.”
Augustine, City of God, Book 12, 3
Taylor Marshall is the Adjunct Instructor in Philosophy at the University of Dallas. 
Aristotle called the philosophy of being "first philosophy" because it does not examine the parts of reality (politics, math, music, history), but reality itself: existence, change, properties, space, time, causality, and possibility. This first philosophy is also called "metaphysics," deriving from the Greek words meta ("beyond") and physica ("physical").
I designed this site for students studying philosophy at the College of Saint Thomas More. Whether or not you are taking courses, I hope that you find the articles, outlines, and essays helpful.
Metaphysically,
Dr. Taylor Marshall
Professor of Philosophy
College of Saint Thomas More
“for this expressed very exactly be essentia.”
Is this a typo? The sentence doesn’t make much sense…