Full Idea
A 'set' is a mathematically well-behaved class.
Gist of Idea
A 'set' is a mathematically well-behaved class
Source
Wilfrid Hodges (First-Order Logic [2001], 1.6)
Book Reference
'Blackwell Guide to Philosophical Logic', ed/tr. Goble,Lou [Blackwell 2001], p.19