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Wellsprings
metaphysics

Essence

τὸ τί ἦν εἶναι

Not just what a thing is, but what it is to be that thing — its very whatness.

Aristotle developed the concept of essence—what something fundamentally is—as central to his metaphysics. The essence of a thing is what makes it that particular thing rather than something else. It is not merely its size, qualities, or capacities, but rather its underlying nature that remains constant. Aristotle argued that knowing the essence means knowing the definition that captures what that thing truly is. For example, the essence of a human is what makes a human a human, not simply being tall or capable of reasoning.

This concept becomes concrete when we consider how we define things. If you claim that being human is the same as being non-human, you have contradicted the very notion of essence—essence must be stable and singular. The definition that expresses essence, which Aristotle called the formula, reveals the substance of each individual thing. This framework allows us to distinguish genuine knowledge of what something is from mere observation of its accidental properties.

Where this idea shows up

47 Greek sources

Where to read it