Combining Texts

Ideas for 'Logicism and Ontological Commits. of Arithmetic', 'Knowing One's Own Mind' and 'Could There Be Unicorns?'

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5 ideas

4. Formal Logic / D. Modal Logic ML / 1. Modal Logic

16951

It was realised that possible worlds covered all modal logics, if they had a structure [Dummett]

4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / a. Systems of modal logic

16952

If something is only possible relative to another possibility, the possibility relation is not transitive [Dummett]

16953

Relative possibility one way may be impossible coming back, so it isn't symmetrical [Dummett]

4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / d. System T

16960

If possibilitiy is relative, that might make accessibility non-transitive, and T the correct system [Dummett]

4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / g. System S4

16958

In S4 the actual world has a special place [Dummett]