Set-theoretic definition of natural numbers - Definition

Set theoretic definition of the natural numbers

John von Neumann proposed the folowing definition:

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

See Peano arithmetic.

References

• What are the Natural Numbers? (http://www.maths.may.ie/staff/gmg/nn.ps), Gary McGuire