The following definition was first published by John von Neumann, although Levy attributes the idea to unpublished work of Zermelo in 1916. As this definition extends to infinite set as a definition of ordinal number, the sets considered below are sometimes called von Neumann ordinals.
the following definition was first published by john von neumann although levy attributes the idea to unpublished work of zermelo in 1916 as this definition extends to infinite set as a definition of ordinal number the sets considered below are sometimes called von neumann ordinals