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All the ideas for 'What is Logic?st1=Ian Hacking', 'Vagueness, Truth and Logic' and 'Commentary on 'Posterior Analytics'

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25 ideas

1. Philosophy / F. Analytic Philosophy / 6. Logical Analysis
9766 Study vagueness first by its logic, then by its truth-conditions, and then its metaphysics [Fine,K]
2. Reason / D. Definition / 3. Types of Definition
13838 A decent modern definition should always imply a semantics [Hacking]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL
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]
13833 'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [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 / D. Assumptions for Logic / 2. Excluded Middle
9775 Excluded Middle, and classical logic, may fail for vague predicates [Fine,K]
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 / I. Semantics of Logic / 3. Logical Truth
9771 Logic holding between indefinite sentences is the core of all language [Fine,K]
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 / 10. Vagueness / d. Vagueness as linguistic
9768 Vagueness is semantic, a deficiency of meaning [Fine,K]
7. Existence / D. Theories of Reality / 10. Vagueness / e. Higher-order vagueness
9776 A thing might be vaguely vague, giving us higher-order vagueness [Fine,K]
7. Existence / D. Theories of Reality / 10. Vagueness / f. Supervaluation for vagueness
9767 A vague sentence is only true for all ways of making it completely precise [Fine,K]
9770 Logical connectives cease to be truth-functional if vagueness is treated with three values [Fine,K]
9772 Meaning is both actual (determining instances) and potential (possibility of greater precision) [Fine,K]
9773 With the super-truth approach, the classical connectives continue to work [Fine,K]
9774 Borderline cases must be under our control, as capable of greater precision [Fine,K]
9. Objects / B. Unity of Objects / 3. Unity Problems / e. Vague objects
9769 Vagueness can be in predicates, names or quantifiers [Fine,K]
18. Thought / E. Abstraction / 8. Abstractionism Critique
9074 Abstraction cannot produce the concept of a 'game', as there is no one common feature [Barnes,J]
9073 Abstraction from an ambiguous concept like 'mole' will define them as the same [Barnes,J]
9072 Defining concepts by abstractions will collect together far too many attributes from entities [Barnes,J]