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All the ideas for 'What is Logic?st1=Ian Hacking', 'The Source of Necessity' and 'A World of States of Affairs'

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21 ideas

2. Reason / D. Definition / 3. Types of Definition
13838 A decent modern definition should always imply a semantics [Hacking]
3. Truth / C. Correspondence Truth / 1. Correspondence Truth
4742 Correspondence may be one-many or many one, as when either p or q make 'p or q' true [Armstrong]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL
13833 'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking]
13834 Gentzen's Cut Rule (or transitivity of deduction) is 'If A |- B and B |- C, then A |- C' [Hacking]
13835 Only Cut reduces complexity, so logic is constructive without it, and it can be dispensed with [Hacking]
5. Theory of Logic / A. Overview of Logic / 4. Pure Logic
13845 The various logics are abstractions made from terms like 'if...then' in English [Hacking]
5. Theory of Logic / A. Overview of Logic / 5. First-Order Logic
13840 First-order logic is the strongest complete compact theory with Löwenheim-Skolem [Hacking]
13844 A limitation of first-order logic is that it cannot handle branching quantifiers [Hacking]
5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic
13842 Second-order completeness seems to need intensional entities and possible worlds [Hacking]
5. Theory of Logic / E. Structures of Logic / 2. Logical Connectives / a. Logical connectives
13837 With a pure notion of truth and consequence, the meanings of connectives are fixed syntactically [Hacking]
5. Theory of Logic / E. Structures of Logic / 4. Variables in Logic
13839 Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers [Hacking]
5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems
13843 If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking]
7. Existence / D. Theories of Reality / 7. Fictionalism
9497 Without modality, Armstrong falls back on fictionalism to support counterfactual laws [Bird on Armstrong]
8. Modes of Existence / B. Properties / 1. Nature of Properties
15550 Properties are contingently existing beings with multiple locations in space and time [Armstrong, by Lewis]
10. Modality / C. Sources of Modality / 1. Sources of Necessity
4743 The truth-maker for a truth must necessitate that truth [Armstrong]
12432 Explanation of necessity must rest on something necessary or something contingent [Hale]
12434 Why is this necessary, and what is necessity in general; why is this necessary truth true, and why necessary? [Hale]
12435 The explanation of a necessity can be by a truth (which may only happen to be a necessary truth) [Hale]
10. Modality / C. Sources of Modality / 3. Necessity by Convention
12433 If necessity rests on linguistic conventions, those are contingent, so there is no necessity [Hale]
10. Modality / C. Sources of Modality / 4. Necessity from Concepts
12436 Concept-identities explain how we know necessities, not why they are necessary [Hale]
26. Natural Theory / C. Causation / 9. General Causation / d. Causal necessity
4798 In recent writings, Armstrong makes a direct identification of necessitation with causation [Armstrong, by Psillos]