Full Idea
Principles must be judged from the point of view of science, and not science from the point of view of principles fixed once and for all. Geometry existed before Euclid's 'Elements', just as arithmetic and set theory did before Peano's 'Formulaire'.
Gist of Idea
We should judge principles by the science, not science by some fixed principles
Source
Ernst Zermelo (New Proof of Possibility of Well-Ordering [1908], §2a)
Book Reference
'From Frege to Gödel 1879-1931', ed/tr. Heijenoort,Jean van [Harvard 1967], p.189
A Reaction
This shows why the axiomatisation of set theory is an ongoing and much-debated activity.