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All the ideas for 'What is Logic?st1=Ian Hacking', 'Review of Frege's 'Grundlagen'' and 'Definitions'

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24 ideas

2. Reason / D. Definition / 1. Definitions
11215 Notable definitions have been of piety (Plato), God (Anselm), number (Frege), and truth (Tarski) [Gupta]
11223 Definitions usually have a term, a 'definiendum' containing the term, and a defining 'definiens' [Gupta]
2. Reason / D. Definition / 2. Aims of Definition
11225 A definition needs to apply to the same object across possible worlds [Gupta]
11227 The 'revision theory' says that definitions are rules for improving output [Gupta]
2. Reason / D. Definition / 3. Types of Definition
13838 A decent modern definition should always imply a semantics [Hacking]
11221 A definition can be 'extensionally', 'intensionally' or 'sense' adequate [Gupta]
11224 Traditional definitions are general identities, which are sentential and reductive [Gupta]
11226 Traditional definitions need: same category, mention of the term, and conservativeness and eliminability [Gupta]
2. Reason / D. Definition / 4. Real Definition
11217 Chemists aim at real definition of things; lexicographers aim at nominal definition of usage [Gupta]
2. Reason / D. Definition / 6. Definition by Essence
11216 If definitions aim at different ideals, then defining essence is not a unitary activity [Gupta]
2. Reason / D. Definition / 10. Stipulative Definition
11218 Stipulative definition assigns meaning to a term, ignoring prior meanings [Gupta]
2. Reason / D. Definition / 11. Ostensive Definition
11220 Ostensive definitions look simple, but are complex and barely explicable [Gupta]
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]
4. Formal Logic / F. Set Theory ST / 6. Ordering in Sets
11222 The ordered pair <x,y> is defined as the set {{x},{x,y}}, capturing function, not meaning [Gupta]
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]
6. Mathematics / B. Foundations for Mathematics / 5. Definitions of Number / c. Fregean numbers
9992 The 'extension of a concept' in general may be quantitatively completely indeterminate [Cantor]