Definition

The demand for definition is the demand for the universal: Socrates' search for what virtue or beauty 'really is' sets the agenda for all subsequent philosophy.

Definition states the essence: genus plus differentia, capturing the universal nature shared by all members of a species — real definition is a truth about things, not a convention about words.

Real definitions express the essence of things; but for immaterial beings like God, strict definition fails and we must resort to analogy and negation.

Definitions are purely verbal: they fix the meanings of names, and the only test of a good definition is internal consistency and avoidance of ambiguity.

Our definitions are of nominal essences only; real essences — the inner constitutions that produce the observable qualities of things — remain largely unknown to us.

Genuine definition does not merely list properties but reveals the efficient or formal cause from which all the thing's properties can be derived.

To define a concept, trace it to the impressions it comes from; any concept that cannot be traced to experience is a confusion masquerading as an idea.

Strict definition is possible only in mathematics; in philosophy, concepts are given before definitions and must be analyzed rather than constructed.

Definitions are of names, not of things; but 'real kinds' in nature impose constraints on which definitions are scientifically fruitful.