Combining Texts

Ideas for 'fragments/reports', 'Introduction to Mathematical Logic' and 'Models and Reality'

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5 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 / o. Axiom of Constructibility V = L

13655

The Löwenheim-Skolem theorems show that whether all sets are constructible is indeterminate [Putnam, by Shapiro]

9915	V = L just says all sets are constructible [Putnam]

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]