Full Idea
Knowledge is independent of experience if any experience which would enable us to acquire the concepts involved would enable us to have the knowledge.
Gist of Idea
Knowledge is a priori if the experience giving you the concepts thus gives you the knowledge
Source
Philip Kitcher (The Nature of Mathematical Knowledge [1984], 01.3)
Book Reference
Kitcher,Philip: 'The Nature of Mathematical Knowledge' [OUP 1984], p.22
A Reaction
This is the 'conceptualist' view of a priori knowledge, which Kitcher goes on to attack, preferring a 'constructivist' view. The formula here shows that we can't divorce experience entirely from a priori thought. I find conceptualism a congenial view.