more from Harold Noonan

Single Idea 16019

[catalogued under 9. Objects / F. Identity among Objects / 8. Leibniz's Law]

Full Idea

Leibniz's Law must be clearly distinguished from the substitutivity principle, that if 'a' and 'b' are codesignators they are substitutable salva veritate.


'Salva veritate' means 'while preserving the truth'

Gist of Idea

Leibniz's Law must be kept separate from the substitutivity principle


Harold Noonan (Identity [2009], 2)

Book Reference

'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [], p.3

A Reaction

He gives a bunch of well-known problem cases for substitutivity. The Morning Star, Giorgione, and the number of planets won't work. Belief contexts, or facts about spelling, may not be substitutable.