Single Idea 13429

[catalogued under 5. Theory of Logic / D. Assumptions for Logic / 4. Identity in Logic]

Full Idea

Wittgenstein discovered that the sign of identity is not a necessary constituent of logical notation, but can be replaced by the convention that different signs must have different meanings.

Gist of Idea

The identity sign is not essential in logical notation, if every sign has a different meaning

Source

report of Ludwig Wittgenstein (Tractatus Logico-Philosophicus [1921]) by Frank P. Ramsey - The Foundations of Mathematics p.139

Book Reference

Ramsey,Frank: 'Philosophical Papers', ed/tr. Mellor,D.H. [CUP 1990], p.194


A Reaction

[Ramsey cites p.139 - need to track down the modern reference] Hence in modern logic it is usually necessary to say that we are using 'classical logic with identity', since the use of identity is very convenient, and reasonably harmless (I think).