Full Idea
The ultimate principles upon which mathematics rests are those to which mathematicians appeal without proof; and the primitive concepts of mathematics ...themselves are grasped directly, if grasped at all, without the mediation of definition.
Gist of Idea
The ultimate principles and concepts of mathematics are presumed, or grasped directly
Source
John Mayberry (What Required for Foundation for Maths? [1994], p.405-1)
Book Reference
'Philosophy of Mathematics: anthology', ed/tr. Jacquette,Dale [Blackwell 2002], p.405
A Reaction
This begs the question of whether the 'grasping' is purely a priori, or whether it derives from experience. I defend the latter, and Jenkins puts the case well.