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  "body": "\n## Summary\n\nA formula of the form (∀α)(∀β)(Abst(α) = Abst(β) ↔ Equ(α, β)), where Abst is an abstraction operator mapping the type of entities ranged over by α and β to objects, and “Equ” is an equivalence relation on the type of entities ranged over by α and β. For instance, Hume's principle, and Basic Law V.\n",
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