Full Idea
In Zermelo's set theory, the Burali-Forti Paradox becomes a proof that there is no set of all ordinals (so 'is an ordinal' has no extension).
Gist of Idea
In ZF, the Burali-Forti Paradox proves that there is no set of all ordinals
Source
report of Ernst Zermelo (Investigations in the Foundations of Set Theory I [1908]) by William D. Hart - The Evolution of Logic 3
Book Reference
Hart,W.D.: 'The Evolution of Logic' [CUP 2010], p.70