more from Gottfried Leibniz

Single Idea 8650

[catalogued under 9. Objects / F. Identity among Objects / 9. Sameness]

Full Idea

Leibniz's definition is as follows: Things are the same as each other, of which one can be substituted for the other without loss of truth ('salva veritate').

Gist of Idea

Things are the same if one can be substituted for the other without loss of truth

Source

Gottfried Leibniz (works [1690]), quoted by Gottlob Frege - Grundlagen der Arithmetik (Foundations) 65

Book Reference

Frege,Gottlob: 'The Foundations of Arithmetic (Austin)', ed/tr. Austin,J.L. [Blackwell 1980], p.76


A Reaction

Frege doesn't give a reference. (Anyone know it?). This famous definition is impressive, but has problems when the items being substituted appear in contexts of belief. 'Oedipus believes Jocasta (his mother!) would make a good wife'.