Single Idea 9585

[catalogued under 4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / e. Axioms of PL]

Full Idea

Since every definition is an equation, one cannot define equality itself.

Gist of Idea

Since every definition is an equation, one cannot define equality itself

Source

Gottlob Frege (Review of Husserl's 'Phil of Arithmetic' [1894], p.327)

Book Reference

-: 'Mind July 1972' [-], p.327


A Reaction

This seems a particularly nice instance of the general rule that 'you have to start somewhere'. It is a nice test case for the nature of meaning to ask 'what do you understand when you understand equality?', given that you can't define it.

Related Idea

Idea 16498 Identity cannot be defined, because definitions are identities [Wiggins]