Full Idea
Each Von Neumann ordinal number is the set of its predecessors. ...He had shown how to introduce ordinal numbers as sets, making it possible to use them without leaving the domain of sets.
Gist of Idea
Each Von Neumann ordinal number is the set of its predecessors
Source
report of John von Neumann (On the Introduction of Transfinite Numbers [1923]) by Shaughan Lavine - Understanding the Infinite V.3
Book Reference
Lavine,Shaughan: 'Understanding the Infinite' [Harvard 1994], p.122