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epistemology

Definition

ὁρισμός

Pinning down exactly what something is by naming its kind and what sets it apart from everything else of that kind.

Horismos, or definition, is the logical method of stating what something fundamentally is by identifying its genus (the broader category it belongs to) and its differentia (the specific features that distinguish it from others in that category). Developed systematically by Aristotle, though championed in inquiry by Socrates, this approach aims to capture the essence of a thing rather than merely listing examples or properties. The method became foundational to Greek philosophical practice and influenced how thinkers approached knowledge itself.

In practice, horismos works by moving from particulars to universals. When Socrates interrogates Euthyphro about holiness, he rejects a mere catalogue of holy acts and instead demands the single unifying character that makes all those acts holy—their common essence. This reflects the conviction that true knowledge requires grasping what something is fundamentally, not just cataloguing what it does or how it appears. Without such definition, the argument goes, we lack genuine understanding.

Where this idea shows up

105 Greek sources

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