Combining Philosophers

All the ideas for Benjamin Constant, C.D. Broad and Wilfrid Hodges

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25 ideas

2. Reason / D. Definition / 7. Contextual Definition
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
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
Since first-order languages are complete, |= and |- have the same meaning [Hodges,W]
5. Theory of Logic / B. Logical Consequence / 4. Semantic Consequence |=
|= 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
A formula needs an 'interpretation' of its constants, and a 'valuation' of its variables [Hodges,W]
There are three different standard presentations of semantics [Hodges,W]
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
|= should be read as 'is a model for' or 'satisfies' [Hodges,W]
5. Theory of Logic / J. Model Theory in Logic / 1. Logical Models
Model theory studies formal or natural language-interpretation using set-theory [Hodges,W]
A 'structure' is an interpretation specifying objects and classes of quantification [Hodges,W]
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
Down Löwenheim-Skolem: if a countable language has a consistent theory, that has a countable model [Hodges,W]
Up Löwenheim-Skolem: if infinite models, then arbitrarily large models [Hodges,W]
5. Theory of Logic / K. Features of Logics / 6. Compactness
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
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
A 'set' is a mathematically well-behaved class [Hodges,W]
9. Objects / E. Objects over Time / 4. Four-Dimensionalism
Surely the past phases of a thing are not parts of the thing? [Broad]
A thing is simply a long event, linked by qualities, and spatio-temporal unity [Broad]
If short-lived happenings like car crashes are 'events', why not long-lived events like Dover Cliffs? [Broad]
12. Knowledge Sources / B. Perception / 6. Inference in Perception
Broad rejects the inferential component of the representative theory [Broad, by Maund]
24. Political Theory / D. Ideologies / 6. Liberalism / b. Liberal individualism
Liberty is the triumph of the individual, over both despotic government and enslaving majorities [Constant]
24. Political Theory / D. Ideologies / 6. Liberalism / c. Liberal equality
Minority rights are everyone's rights, because we all have turns in the minority [Constant]
27. Natural Reality / D. Time / 1. Nature of Time / g. Growing block
The present and past exist, but the future does not [Broad, by Dummett]
We could say present and past exist, but not future, so that each event adds to the total history [Broad]
27. Natural Reality / D. Time / 2. Passage of Time / d. Time series
We imagine the present as a spotlight, moving across events from past to future [Broad]