Last updated on 28 Apr 2022
Liddell and Scott: property; (philosophy) being, essence, reality.
That which is one’s own, one’s property. Substance, as in “a man of substance”.
In philosophy, ousia is taken to mean stable being, substance, or essence [but see arch?, eidos]. When Aristotle introduced the notion of an essence in the Metaphysics Z, he uses a phrase, to ti ên einai , which was translated into Latin as essentia.
The uses of ousia for essence or nature in philosophy are probably derived from the theological Christological debates of the fourth century, in which the eastern and western churches split based on a difference between Jesus divine and human natures being homoiousias (Eastern, or Orthodox churches), meaning “similar natures” or homoousias, (Western or Roman churches) meaning “same nature”. There is literally one iota of difference between them.
In his logical works, Aristotle links the notion of essence to that of definition (horismos)—“a definition is an account (logos) that signifies an essence” (Topics 102a3)—and he links both of these notions to a certain kind of per se predication (kath’ hauto, literally, “in respect of itself,” or “intrinsically“)—”what belongs to a thing in respect of itself belongs to it in its essence (en tôi ti esti)” for we refer to it “in the account that states the essence” (Posterior Analytics, 73a34–5)