Combining Philosophers

Ideas for Rescher,N/Oppenheim,P, Cynthia Macdonald and Gottlob Frege

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10 ideas

4. Formal Logic / F. Set Theory ST / 1. Set Theory
Frege did not think of himself as working with sets [Frege, by Hart,WD]
4. Formal Logic / F. Set Theory ST / 3. Types of Set / b. Empty (Null) Set
The null set is only defensible if it is the extension of an empty concept [Frege, by Burge]
It is because a concept can be empty that there is such a thing as the empty class [Frege, by Dummett]
The null set is indefensible, because it collects nothing [Frege, by Burge]
A class is an aggregate of objects; if you destroy them, you destroy the class; there is no empty class [Frege]
4. Formal Logic / F. Set Theory ST / 3. Types of Set / e. Equivalence classes
We can introduce new objects, as equivalence classes of objects already known [Frege, by Dummett]
Frege introduced the standard device, of defining logical objects with equivalence classes [Frege, by Dummett]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / f. Axiom of Infinity V
Frege, unlike Russell, has infinite individuals because numbers are individuals [Frege, by Bostock]
4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / c. Logical sets
A class is, for Frege, the extension of a concept [Frege, by Dummett]
Frege proposed a realist concept of a set, as the extension of a predicate or concept or function [Frege, by Benardete,JA]