Being as Common in Plato's Theaetetus

Abstract

At Theaetetus 185a-186e, Plato has Socrates describe being (οὐσία) as a common (κοινόν) feature in all things. This is among the Western canon's earliest references to being as such and scholars debate its meaning. Recent commentators understand “being” as existence, the condition for veridical correspondence, or other notions popular in contemporary philosophy. The meaning of “being” in the passage, however, is more Platonic and hence far stranger, concerning spatiotemporal things’ derivation from causally prior determinate sources (i.e., forms). Further uses of οὐσία in the Theaetetus (207b4-c4) show that being is a singular, formal principle of determinate unity in all beings.