Full Idea
Substitutionalists simulate quantification over fictional characters by quantifying for real over fictional names.
Gist of Idea
We can quantify over fictions by quantifying for real over their names
Source
David Lewis (Noneism or Allism? [1990], p.159)
Book Reference
Lewis,David: 'Papers in Metaphysics and Epistemology' [CUP 1999], p.159
A Reaction
I would say that a fiction is a file of conceptual information, identified by a label. The label brings baggage with it, and there is no existence in the label.