Ideas from 'Could There Be Unicorns?' by Michael Dummett [1983], by Theme Structure

[found in 'The Seas of Language' by Dummett,Michael [OUP 1993,0-19-823621-2]].

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4. Formal Logic / D. Modal Logic ML / 1. Modal Logic
It was realised that possible worlds covered all modal logics, if they had a structure
4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / a. Systems of modal logic
If something is only possible relative to another possibility, the possibility relation is not transitive
Relative possibility one way may be impossible coming back, so it isn't symmetrical
4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / d. System T
If possibilitiy is relative, that might make accessibility non-transitive, and T the correct system
4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / g. System S4
In S4 the actual world has a special place
9. Objects / D. Essence of Objects / 10. Essence as Species
Kripke says internal structure fixes species; I say it is genetic affinity and a common descent
10. Modality / E. Possible worlds / 1. Possible Worlds / a. Possible worlds
Possible worlds aren't how the world might be, but how a world might be, given some possibility
10. Modality / E. Possible worlds / 1. Possible Worlds / c. Possible worlds realism
If possible worlds have no structure (S5) they are equal, and it is hard to deny them reality
23. Ethics / C. Virtue Theory / 1. Virtue Theory / d. Virtue theory critique
To explain generosity in a person, you must understand a generous action
26. Natural Theory / B. Concepts of Nature / 6. Natural Kinds / g. Critique of kinds
Generalised talk of 'natural kinds' is unfortunate, as they vary too much