While the existence of inductive sets is ensured by the axiom of infinity, there is one particular inductive set worth a closer look - the minimal inductive set. We can use the axiom of separation, to define it uniquely:
The set $\omega:=\{W\mid \forall X(X\text{ is an inductive set }\Rightarrow W\in X)\}$ is the minimal set, which fulfills the axiom of infinity. It is called the minimal inductive set.
Corollaries: 1
Definitions: 2 3
Examples: 4
Explanations: 5
Proofs: 6