Combining Texts

All the ideas for 'Later Letters to Dedekind', 'Morality and Art' and 'Logical Necessity'

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17 ideas

4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5
12204 The logic of metaphysical necessity is S5 [Rumfitt]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / a. Axioms for sets
17831 Cantor gives informal versions of ZF axioms as ways of getting from one set to another [Cantor, by Lake]
5. Theory of Logic / B. Logical Consequence / 1. Logical Consequence
12195 Soundness in argument varies with context, and may be achieved very informally indeed [Rumfitt]
12199 There is a modal element in consequence, in assessing reasoning from suppositions [Rumfitt]
12201 We reject deductions by bad consequence, so logical consequence can't be deduction [Rumfitt]
5. Theory of Logic / D. Assumptions for Logic / 3. Contradiction
12194 Contradictions include 'This is red and not coloured', as well as the formal 'B and not-B' [Rumfitt]
5. Theory of Logic / H. Proof Systems / 2. Axiomatic Proof
12198 Geometrical axioms in logic are nowadays replaced by inference rules (which imply the logical truths) [Rumfitt]
10. Modality / A. Necessity / 3. Types of Necessity
14532 A distinctive type of necessity is found in logical consequence [Rumfitt, by Hale/Hoffmann,A]
10. Modality / A. Necessity / 6. Logical Necessity
12193 Logical necessity is when 'necessarily A' implies 'not-A is contradictory' [Rumfitt]
12200 A logically necessary statement need not be a priori, as it could be unknowable [Rumfitt]
12202 Narrow non-modal logical necessity may be metaphysical, but real logical necessity is not [Rumfitt]
10. Modality / E. Possible worlds / 1. Possible Worlds / e. Against possible worlds
12203 If a world is a fully determinate way things could have been, can anyone consider such a thing? [Rumfitt]
22. Metaethics / A. Ethics Foundations / 1. Nature of Ethics / b. Defining ethics
22445 Morality shows murder is wrong, but not what counts as a murder [Foot]
22. Metaethics / A. Ethics Foundations / 1. Nature of Ethics / c. Purpose of ethics
22444 A moral system must deal with the dangers and benefits of life [Foot]
22. Metaethics / B. Value / 1. Nature of Value / c. Objective value
22447 Saying something 'just is' right or wrong creates an illusion of fact and objectivity [Foot]
23. Ethics / D. Deontological Ethics / 6. Motivation for Duty
22448 We sometimes just use the word 'should' to impose a rule of conduct on someone [Foot]
25. Social Practice / F. Life Issues / 3. Abortion
22446 In the case of something lacking independence, calling it a human being is a matter of choice [Foot]