What is Ousia?

What is Ousia?
Ousia, or in the Greek "οὐσία", is a term Christians adopted by Greek philosophers such as Aristotle and Plato who used the term to speak of substance or essence, and early Christians did the same; however, they used it more commonly to refer to the Trinity, creating the phrase: "θεία ουσία" or, divine essence. God's essence and nature is Ousia. When we say God is one in essence or unity, we are saying he is one in Ousia. 

As one church father wrote: "The distinction between οὐσία (ousia) and ὑ πόστασις (hypostasis) is the same as that between the general and the particular; as, for instance, between the animal and the particular man. Wherefore, in the case of the Godhead, we confess one essence or substance so as not to give a variant definition of existence, but we confess a particular hypostasis, in order that our conception of Father, Son and Holy Spirit may be without confusion and clear. If we have no distinct perception of the separate characteristics, namely, fatherhood, sonship, and sanctification, but form our conception of God from the general idea of existence, we cannot possibly give a sound account of our faith," (St. Basil of Caesarea, letter 236, §6).

Works Cited:

Bridge, James. "Homoousion." The Catholic Encyclopedia. Vol. 7. New York: Robert Appleton Company, 1910. http://www.newadvent.org/cathen/07449a.htm.

"ousia." Definitions.net. STANDS4 LLC, 2023. Web. 8 Dec. 2023. https://www.definitions.net/definition/ousia.

“Ousia.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/ousia. Accessed 8 Dec. 2023.

Lienhard, Joseph T., 'Ousia and Hypostasis: The Cappadocian Settlement and the Theology of ‘One Hypostasis’', in Stephen T. Davis, Daniel Kendall SJ, and Gerald O'Collins SJ (eds), The Trinity: An Interdisciplinary Symposium on the Trinity (Oxford, 2002; online edn, Oxford Academic, 1 Nov. 2003), https://doi.org/10.1093/0199246122.003.0005, accessed 8 Dec. 2023.

Translated by Blomfield Jackson. From Nicene and Post-Nicene Fathers, Second Series, Vol. 8. Edited by Philip Schaff and Henry Wace. (Buffalo, NY: Christian Literature Publishing Co., 1895.) Revised and edited for New Advent by Kevin Knight. http://www.newadvent.org/fathers/3202236.htm.