quiddity

Quiddity is a term used in philosophy and literary criticism to denote the intrinsic nature or essence of a thing—the “whatness” that defines its identity. It refers to the set of defining properties that make an entity what it is, beyond its particular existence or accidental attributes.

Originating from the Latin quidditas meaning “whatness,” the word entered English through medieval scholastic writers. In that tradition, quiddity distinguished the form or essence of a thing from its matter or its existence, and it was often treated alongside haecceity (the “thisness” that signals individual uniqueness).

In philosophy, quiddity is associated with ontology and the study of substance. It designates the universal form that characterizes a class of things—for example, the quiddity of a human being as a rational animal—while separate from a particular instantiation of that form. The term has been used to contrast essence with existence and with the various accidents or contingent properties a thing might have.

Today, quiddity is less common in ordinary discourse and is often replaced by “essence” or “nature.” When used, it tends to carry a scholarly or historical tone, aiming to capture the defining core or core identity of a thing rather than its transient attributes.

See also: haecceity, essence, ontology, Aristotelianism.