Combining Texts

All the ideas for 'Letters to a German Princess', 'The Foundations of Mathematics (2nd ed)' and 'works'

expand these ideas     |    start again     |     specify just one area for these texts

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4 ideas

4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5

7791	The simplest of the logics based on possible worlds is Lewis's S5 [Lewis,CI, by Girle]

8. Modes of Existence / A. Relations / 4. Formal Relations / b. Equivalence relation

18465

An 'equivalence' relation is one which is reflexive, symmetric and transitive [Kunen]

10. Modality / A. Necessity / 2. Nature of Necessity

11002

Equating necessity with informal provability is the S4 conception of necessity [Lewis,CI, by Read]

26. Natural Theory / D. Laws of Nature / 1. Laws of Nature

5467	Euler said nature is instrinsically passive, and minds cause change [Euler, by Ellis]