Combining Philosophers

All the ideas for Peter Unger, Wilfrid Hodges and Xenophanes

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27 ideas

2. Reason / D. Definition / 7. Contextual Definition
10476 The idea that groups of concepts could be 'implicitly defined' was abandoned [Hodges,W]
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 / A. Overview of Logic / 5. First-Order Logic
10478 Since first-order languages are complete, |= and |- have the same meaning [Hodges,W]
5. Theory of Logic / B. Logical Consequence / 4. Semantic Consequence |=
10477 |= in model-theory means 'logical consequence' - it holds in all models [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 / I. Semantics of Logic / 4. Satisfaction
10474 |= should be read as 'is a model for' or 'satisfies' [Hodges,W]
5. Theory of Logic / J. Model Theory in Logic / 1. Logical Models
10473 Model theory studies formal or natural language-interpretation using set-theory [Hodges,W]
10475 A 'structure' is an interpretation specifying objects and classes of quantification [Hodges,W]
10481 Models in model theory are structures, not sets of descriptions [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 / A. Nature of Mathematics / 5. The Infinite / i. Cardinal infinity
10480 First-order logic can't discriminate between one infinite cardinal and another [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]
7. Existence / D. Theories of Reality / 10. Vagueness / d. Vagueness as linguistic
9052 Vague predicates lack application; there are no borderline cases; vague F is not F [Unger, by Keefe/Smith]
9. Objects / A. Existence of Objects / 5. Simples
16070 There are no objects with proper parts; there are only mereological simples [Unger, by Wasserman]
13. Knowledge Criteria / C. External Justification / 6. Contextual Justification / b. Invariantism
8724 The meaning of 'know' does not change from courtroom to living room [Unger]
13. Knowledge Criteria / D. Scepticism / 1. Scepticism
411 If we succeed in speaking the truth, we cannot know we have done it [Xenophanes]
8722 No one knows anything, and no one is ever justified or reasonable [Unger]
13. Knowledge Criteria / D. Scepticism / 4. Demon Scepticism
8723 An evil scientist may give you a momentary life, with totally false memories [Unger]
13. Knowledge Criteria / E. Relativism / 1. Relativism
412 If God had not created honey, men would say figs are sweeter [Xenophanes]
26. Natural Theory / A. Speculations on Nature / 6. Early Matter Theories / e. The One
1640 The basic Eleatic belief was that all things are one [Xenophanes, by Plato]
28. God / A. Divine Nature / 2. Divine Nature
3055 Xenophanes said the essence of God was spherical and utterly inhuman [Xenophanes, by Diog. Laertius]
28. God / C. Attitudes to God / 5. Atheism
408 Ethiopian gods have black hair, and Thracian gods have red hair [Xenophanes]
407 Mortals believe gods are born, and have voices and clothes just like mortals [Xenophanes]