Single Idea 4960

[catalogued under 10. Modality / D. Knowledge of Modality / 3. A Posteriori Necessary]

Full Idea

An identity statement between names (such as 'Hesperus' and 'Phosphorus'), when true at all, is necessarily true, even though one may not know it a priori.

Clarification

Hesperus (the evening star) and Phosphorus (the morning star) turned out to be the planet Venus

Gist of Idea

"'Hesperus' is 'Phosphorus'" is necessarily true, if it is true, but not known a priori

Source

Saul A. Kripke (Naming and Necessity lectures [1970], Lecture 3)

Book Reference

Kripke,Saul: 'Naming and Necessity' [Blackwell 1980], p.108


A Reaction

This seems correct, but one should not read too much into it. What should we say if Venus fissions into two, one for the morning, one for the evening? That identity implies x=x doesn't prove the existence of unchanging essences.