Definition:Minimally Inductive Set/Definition 2

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The minimally inductive set $\omega$ is defined as the set of all finite ordinals:

$\omega := \set {\alpha: \alpha \text{ is a finite ordinal} }$


The name minimally inductive set is borrowed from the concept of the minimally inductive class as introduced by Raymond M. Smullyan and Melvin Fitting in their Set Theory and the Continuum Problem.

Keith Devlin, in The Joy of Sets: Fundamentals of Contemporary Set Theory, refers to this object as the first infinite ordinal.

Paul Halmos raises the concept in his Naive Set Theory, but fails to pin a name to it.

The term minimal infinite successor set was invented by $\mathsf{Pr} \infty \mathsf{fWiki}$ in an attempt to provide a name consistent and compatible with Halmos's approach.

As such, it is not generally expected to be seen in this context outside $\mathsf{Pr} \infty \mathsf{fWiki}$.

Instances of this term have subsequently been replaced by minimally inductive set.

Also see

  • Results about the minimally inductive set can be found here.