Full Idea
Mathematics reduces only to set theory, and not to logic proper… but set theory cannot claim the same firmness and obviousness as logic.
Gist of Idea
Mathematics reduces to set theory (which is a bit vague and unobvious), but not to logic proper
Source
Willard Quine (Epistemology Naturalized [1968], p.69-70)
Book Reference
Quine,Willard: 'Ontological Relativity and Other Essays' [Columbia 1969], p.69