Full Idea
'Necessarily 9>7' may be true while the sentence 'necessarily the number of planets < 7' is false, even though it is obtained by substituting a coreferential term. So quantification in these contexts is unintelligible, without a clear object.
Gist of Idea
We can't quantify in modal contexts, because the modality depends on descriptions, not objects
Source
report of Willard Quine (Reference and Modality [1953]) by Kit Fine - Intro to 'Modality and Tense' p. 4
Book Reference
Fine,Kit: 'Modality and Tense' [OUP 2005], p.4
A Reaction
This is Quine's second argument against modality. See Idea 9201 for his first. Fine attempts to refute it. The standard reply seems to be to insist that 9 must therefore be an object, which pushes materialist philosophers into reluctant platonism.
Related Idea
Idea 9201 Whether 9 is necessarily greater than 7 depends on how '9' is described [Quine, by Fine,K]