Full Idea
People have asked me, 'How can you, a nominalist, do work in set theory and in logic, which are theories about things you do not believe in?' ...I believe that there is a value even in fairy tales and the study of fairy tales.
Gist of Idea
Set theory and logic are fairy tales, but still worth studying
Source
Alfred Tarski (talk [1965]), quoted by Feferman / Feferman - Alfred Tarski: life and logic
Book Reference
Feferman,S/Feferman,A.B.: 'Alfred Tarski: life and logic' [CUP 2008], p.52
A Reaction
This is obviously an oversimplification. I don't think for a moment that Tarski literally believed that the study of fairy tales had as much value as the study of logic. Why do we have this particular logic, and not some other?