Combining Texts

All the ideas for 'fragments/reports', 'Set Theory and the Continuum Hypothesis' and 'First-Order Logic'

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11 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]
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / a. Constructivism
14248 We could accept the integers as primitive, then use sets to construct the rest [Cohen]
19. Language / B. Reference / 1. Reference theories
1757 The Electra: she knows this man, but not that he is her brother [Eucleides, by Diog. Laertius]
22. Metaethics / C. The Good / 1. Goodness / b. Types of good
3028 The chief good is unity, sometimes seen as prudence, or God, or intellect [Eucleides]