Full Idea
The inferential role of the existential quantifier in first order logic does not carry over to the existential quantifier in English (we have empty names, singular terms that are not even in the business of denoting, and so on).
Gist of Idea
The quantifier in logic is not like the ordinary English one (which has empty names, non-denoting terms etc)
Source
Thomas Hofweber (Ambitious, yet modest, Metaphysics [2009], 2)
Book Reference
'Metametaphysics', ed/tr. Chalmers/Manley/Wasserman [OUP 2009], p.274