Full Idea
Frege saw arithmetical judgements as resting on a foundation of logical principles, and the discovery of this foundation as a discovery of the nature and structure of the justification of arithmetical truths and judgments.
Gist of Idea
Frege aimed to discover the logical foundations which justify arithmetical judgements
Source
report of Gottlob Frege (works [1890]) by Tyler Burge - Frege on Knowing the Foundations Intro
Book Reference
Burge,Tyler: 'Truth, Thought, Reason (on Frege)' [OUP 2001], p.317
A Reaction
Burge's point is that the logic justifies the arithmetic, as well as underpinning it.