Set-theoretic definition of natural numbers

Set theoreticetic definition of the natural numbers

Consider this a prelimenary draft. I thought this article is called for, but I do not see myself an authority on the subject. -- yish

John von Neumann proposed the folowing definition:

1. Define the empty set to be zero.
2. Define the successor of n as n ∪ {n}

References

• [What are the Natural Numbers?], Gary McGuire