Full Idea
It is well known that virtually every field of mathematics can be reduced to, or modelled in, set theory.
Gist of Idea
Virtually all of mathematics can be modeled in set theory
Source
Stewart Shapiro (Philosophy of Mathematics [1997], Intro)
Book Reference
Shapiro,Stewart: 'Philosophy of Mathematics:structure and ontology' [OUP 1997], p.5
A Reaction
The word 'virtually' is tantalising. The fact that something can be 'modeled' in set theory doesn't mean it IS set theory. Most weather can be modeled in a computer.