Full Idea
For a nominalist with an ontology of empirically distinguishable objects, proper names are seen as a primary vehicle of reference.
Gist of Idea
Nominalists see proper names as a main vehicle of reference
Source
Ruth Barcan Marcus (Nominalism and Substitutional Quantifiers [1978], p.162)
Book Reference
'Philosophy of Logic: an anthology', ed/tr. Jacquette,Dale [Blackwell 2002], p.162