Combining Texts

All the ideas for 'Lectures on Ethics', 'First-Order Logic' and 'Essence and Potentiality'

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17 ideas

5. Theory of Logic / A. Overview of Logic / 1. Overview of Logic
10282 Logic is the study of sound argument, or of certain artificial languages (or applying the latter to the former) [Hodges,W]
5. Theory of Logic / I. Semantics of Logic / 1. Semantics of Logic
10283 A formula needs an 'interpretation' of its constants, and a 'valuation' of its variables [Hodges,W]
10284 There are three different standard presentations of semantics [Hodges,W]
10285 I |= φ means that the formula φ is true in the interpretation I [Hodges,W]
5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems
10288 Down Löwenheim-Skolem: if a countable language has a consistent theory, that has a countable model [Hodges,W]
10289 Up Löwenheim-Skolem: if infinite models, then arbitrarily large models [Hodges,W]
5. Theory of Logic / K. Features of Logics / 6. Compactness
10287 If a first-order theory entails a sentence, there is a finite subset of the theory which entails it [Hodges,W]
6. Mathematics / B. Foundations for Mathematics / 6. Mathematics as Set Theory / a. Mathematics is set theory
10286 A 'set' is a mathematically well-behaved class [Hodges,W]
8. Modes of Existence / C. Powers and Dispositions / 4. Powers as Essence
17954 Essence is a thing's necessities, but what about its possibilities (which may not be realised)? [Vetter]
9. Objects / D. Essence of Objects / 4. Essence as Definition
17953 Real definition fits abstracta, but not individual concrete objects like Socrates [Vetter]
9. Objects / D. Essence of Objects / 7. Essence and Necessity / a. Essence as necessary properties
17952 Modal accounts make essence less mysterious, by basing them on the clearer necessity [Vetter]
10. Modality / A. Necessity / 5. Metaphysical Necessity
17959 Metaphysical necessity is even more deeply empirical than Kripke has argued [Vetter]
10. Modality / B. Possibility / 1. Possibility
17955 Possible worlds allow us to talk about degrees of possibility [Vetter]
17957 Maybe possibility is constituted by potentiality [Vetter]
10. Modality / D. Knowledge of Modality / 4. Conceivable as Possible / c. Possible but inconceivable
17958 The apparently metaphysically possible may only be epistemically possible [Vetter]
10. Modality / E. Possible worlds / 1. Possible Worlds / a. Possible worlds
17956 Closeness of worlds should be determined by the intrinsic nature of relevant objects [Vetter]
25. Social Practice / F. Life Issues / 4. Suicide
19739 The maxim for suicide is committed to the value of life, and is thus contradictory [Kant]