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Ideas for 'What is Logic?st1=Ian Hacking', 'On the Reality of Accidents' and 'works'

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6 ideas

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]

4. Formal Logic / F. Set Theory ST / 1. Set Theory

13455

Frege did not think of himself as working with sets [Frege, by Hart,WD]

4. Formal Logic / F. Set Theory ST / 3. Types of Set / b. Empty (Null) Set

16895

The null set is indefensible, because it collects nothing [Frege, by Burge]

4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / c. Logical sets

3328	Frege proposed a realist concept of a set, as the extension of a predicate or concept or function [Frege, by Benardete,JA]