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Wellsprings
metaphysics

Substance

οὐσία

The independent reality that has properties but is never itself a property of anything else.

Ousia, or substance, names what Aristotle identified as the most fundamental level of reality—that which exists in its own right rather than as a property of something else. For Aristotle, substances are primary because they alone have independent existence; other things like color or size exist only as attributes of substances. A human being is a substance; whiteness or tallness are not, since they depend on something else to exist.

The concept creates a hierarchy of reality itself. Aristotle argued that simpler entities like points and units are more truly substance than complex bodies, since they are not dependent on anything simpler. This reverses intuition: the physical object in front of you seems more real than a mathematical point, yet the point has a kind of logical priority because it is not composed of or dependent upon anything more basic. The question of what truly exists—what the substances of things really are—remained a philosophical puzzle even in antiquity.

Where this idea shows up

35 Greek sources·2 Jewish-canon citations

Where to read it