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All the ideas for 'What is Logic?st1=Ian Hacking', 'Reply to Sixth Objections' and 'Prior Analytics'

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29 ideas

2. Reason / D. Definition / 3. Types of Definition
13838 A decent modern definition should always imply a semantics [Hacking]
4. Formal Logic / A. Syllogistic Logic / 1. Aristotelian Logic
22271 Aristotle was the first to use schematic letters in logic [Aristotle, by Potter]
11060 Aristotelian syllogisms are three-part, subject-predicate, existentially committed, with laws of thought [Aristotle, by Hanna]
18909 Aristotelian sentences are made up by one of four 'formative' connectors [Aristotle, by Engelbretsen]
8080 Aristotelian identified 256 possible syllogisms, saying that 19 are valid [Aristotle, by Devlin]
13912 Aristotle replaced Plato's noun-verb form with unions of pairs of terms by one of four 'copulae' [Aristotle, by Engelbretsen/Sayward]
8071 Aristotle listed nineteen valid syllogisms (though a few of them were wrong) [Aristotle, by Devlin]
4. Formal Logic / A. Syllogistic Logic / 2. Syllogistic Logic
13819 Aristotle's said some Fs are G or some Fs are not G, forgetting that there might be no Fs [Bostock on Aristotle]
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 / D. Modal Logic ML / 4. Alethic Modal Logic
9403 There are three different deductions for actual terms, necessary terms and possible terms [Aristotle]
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 / B. Logical Consequence / 3. Deductive Consequence |-
11148 Deduction is when we suppose one thing, and another necessarily follows [Aristotle]
5. Theory of Logic / E. Structures of Logic / 1. Logical Form
18896 Aristotle places terms at opposite ends, joined by a quantified copula [Aristotle, by Sommers]
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 / E. Structures of Logic / 7. Predicates in Logic
3300 Aristotle's logic is based on the subject/predicate distinction, which leads him to substances and properties [Aristotle, by Benardete,JA]
5. Theory of Logic / G. Quantification / 1. Quantification
11149 Affirming/denying sentences are universal, particular, or indeterminate [Aristotle]
5. Theory of Logic / G. Quantification / 3. Objectual Quantification
8079 Aristotelian logic has two quantifiers of the subject ('all' and 'some') [Aristotle, by Devlin]
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 / C. Structure of Existence / 5. Supervenience / c. Significance of supervenience
3644 Two things being joined together doesn't prove they are the same [Descartes]
10. Modality / A. Necessity / 4. De re / De dicto modality
14641 A deduction is necessary if the major (but not the minor) premise is also necessary [Aristotle]
13. Knowledge Criteria / D. Scepticism / 3. Illusion Scepticism
3621 Only judgement decides which of our senses are reliable [Descartes]
15. Nature of Minds / C. Capacities of Minds / 5. Generalisation by mind
18911 Linguistic terms form a hierarchy, with higher terms predicable of increasing numbers of things [Aristotle, by Engelbretsen]
28. God / A. Divine Nature / 6. Divine Morality / d. God decrees morality
3637 Ideas in God's mind only have value if he makes it so [Descartes]