Full Idea
For Quine, we cannot sensibly ask which is the real number five, the Frege-Russell set or the Von Neumann one. There is no arithmetical or empirical way of deciding between the two. Reference is inscrutable.
Gist of Idea
Reference is inscrutable, because we cannot choose between theories of numbers
Source
report of Willard Quine (Ontological Relativity [1968]) by Alex Orenstein - W.V. Quine Ch.3
Book Reference
Orenstein,Alex: 'W.V. Quine' [Princeton 2002], p.68
A Reaction
To generalise from a problem of reference in the highly abstract world of arithmetic, and say that all reference is inscrutable, strikes me as implausible.