Full Idea
For Frege (as opposed to Gödel) the epistemological aim is not to relate to the objects which are the subject-matter of number theory, but to relate to the states of affairs that make for the truth of number-theoretic statements.
Gist of Idea
We need to grasp not number-objects, but the states of affairs which make number statements true
Source
report of Gottlob Frege (Grundlagen der Arithmetik (Foundations) [1884]) by Crispin Wright - Frege's Concept of Numbers as Objects 1.v
Book Reference
Wright,Crispin: 'Frege's Conception of Numbers' [Scots Philosophical Monographs 1983], p.25
A Reaction
I am beginning to see that this is a key issue in modern philosophy, of whether we build our metaphysics on the things of the world or on the truths about the world. I vote for the things, because the other way slides into anti-realism.