Combining Philosophers

All the ideas for Xenophon, Augustus De Morgan and Michael Hallett

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9 ideas

4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / a. Axioms for sets

17833

The first-order ZF axiomatisation is highly non-categorical [Hallett,M]

17834

Non-categoricity reveals a sort of incompleteness, with sets existing that the axioms don't reveal [Hallett,M]

4. Formal Logic / F. Set Theory ST / 7. Natural Sets

17837

Zermelo allows ur-elements, to enable the widespread application of set-theory [Hallett,M]

5. Theory of Logic / E. Structures of Logic / 6. Relations in Logic

17744

De Morgan started the study of relations and their properties [De Morgan, by Walicki]

13501

De Morgan found inferences involving relations, which eluded Aristotle's syllogistic [De Morgan, by Hart,WD]

5. Theory of Logic / G. Quantification / 2. Domain of Quantification

17743

De Morgan introduced a 'universe of discourse', to replace Boole's universe of 'all things' [De Morgan, by Walicki]

6. Mathematics / A. Nature of Mathematics / 5. The Infinite / g. Continuum Hypothesis

17836

The General Continuum Hypothesis and its negation are both consistent with ZF [Hallett,M]

22. Metaethics / B. Value / 2. Values / h. Fine deeds

5845	Niceratus learnt the whole of Homer by heart, as a guide to goodness [Xenophon]

25. Social Practice / E. Policies / 5. Education / b. Education principles

5833	Education is the greatest of human goods [Xenophon]