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4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / h. Axiom of Replacement VII

[axiom saying the bijection of any set is also a set]

5 ideas
Replacement was added when some advanced theorems seemed to need it [Zermelo, by Maddy]
Fraenkel added Replacement, to give a theory of ordinal numbers [Enderton]
Do the Replacement Axioms exceed the iterative conception of sets? [Boolos, by Maddy]
Replacement: ∀x∈A ∃!y φ(x,y) → ∃Y ∀X∈A ∃y∈Y φ(x,y) [Kunen]
Replacement was immediately accepted, despite having very few implications [Lavine]