Full Idea
The first-order Sermelo-Fraenkel axiomatisation is highly non-categorical.
Gist of Idea
The first-order ZF axiomatisation is highly non-categorical
Source
Michael Hallett (Introduction to Zermelo's 1930 paper [1996], p.1213)
Book Reference
'From Kant to Hilbert: sourcebook Vol. 2', ed/tr. Ewald,William [OUP 1996], p.1213