Sets play a key role in foundations of mathematics. Why? To what extent is it an accident of history? Imagine that you have
a chance to talk to mathematicians from a far-away planet. Would their mathematics be set-based? What are the alternatives
to the set-theoretic foundation of mathematics? Besides, set theory seems to play a significant role in computer science;
is there a good justification for that? We discuss these and some related issues.
This is a revised version of an article originally published in the Bulletin of the European Association for Theoretical Computer
Science, Number 84, October 2004, and republished here with permission of the Association.