Full Idea
I cannot think of any possible evidence that would be regarded as relevant by both nominalists and realists about numbers, and would decide the controversy, or make one side more probable. Hence I regard the external questions as pseudo-questions.
Gist of Idea
No possible evidence could decide the reality of numbers, so it is a pseudo-question
Source
Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 4)
Book Reference
Carnap,Rudolph: 'Meaning and Necessity (2nd ed)' [Chicago 1988], p.219