Combining Philosophers

Ideas for Hermarchus, Michal Walicki and Bernard Linsky

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4 ideas

4. Formal Logic / F. Set Theory ST / 3. Types of Set / b. Empty (Null) Set

17752

The empty set is useful for defining sets by properties, when the members are not yet known [Walicki]

17753

The empty set avoids having to take special precautions in case members vanish [Walicki]

4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / p. Axiom of Reducibility

21705

Reducibility says any impredicative function has an appropriate predicative replacement [Linsky,B]

4. Formal Logic / F. Set Theory ST / 6. Ordering in Sets

17759

Ordinals play the central role in set theory, providing the model of well-ordering [Walicki]