On natural number objects, finiteness and Kripke-Platek models in toposes
The authors show that the existence of a Kripke-Platek model after \textit{J. Barwise} [Admissible sets and structures (1975; Zbl 0316.02047)] in an elementary topos \({\mathcal E}\) is equivalent to the existence of a natural number object in \({\mathcal E}\).
scientific article; zbMATH DE number 4122190
scientific article