Full Idea
In the evaluation of de dicto modal statements, whether some possible state of affairs is relevant to its truth does not depend on the identity of its objects, as in 'Necessarily, the President of the USA is male'.
Gist of Idea
Evaluation of de dicto modalities does not depend on the identity of its objects
Source
Alan Sidelle (Necessity, Essence and Individuation [1989], Ch.3)
Book Reference
Sidelle,Alan: 'Necessity, Essence and Individuation' [Cornell 1989], p.73
A Reaction
This is a more clear-cut and easy to grasp criterion than most that are on offer.