Full Idea
Our set-theoretic methods track the underlying contours of mathematical depth. ...What sets are, most fundamentally, is markers for these contours ...they are maximally effective trackers of certain trains of mathematical fruitfulness.
Gist of Idea
Set-theory tracks the contours of mathematical depth and fruitfulness
Source
Penelope Maddy (Defending the Axioms [2011], 3.4)
Book Reference
Maddy,Penelope: 'Defending the Axioms' [OUP 2013], p.82
A Reaction
This seems to make it more like a map of mathematics than the actual essence of mathematics.