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All the ideas for 'What is Logic?st1=Ian Hacking', 'Conceptual truth and metaphysical necessity' and 'No Moral Difference'

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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]
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 / 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]
10. Modality / C. Sources of Modality / 4. Necessity from Concepts
16423 Conceptual possibilities are metaphysical possibilities we can conceive of [Stalnaker]
16422 The necessity of a proposition concerns reality, not our words or concepts [Stalnaker]
10. Modality / D. Knowledge of Modality / 3. A Posteriori Necessary
16421 Critics say there are just an a priori necessary part, and an a posteriori contingent part [Stalnaker]
10. Modality / E. Possible worlds / 1. Possible Worlds / a. Possible worlds
16429 A 'centred' world is an ordered triple of world, individual and time [Stalnaker]
18. Thought / C. Content / 6. Broad Content
16428 Meanings aren't in the head, but that is because they are abstract [Stalnaker]
19. Language / B. Reference / 3. Direct Reference / b. Causal reference
16432 One view says the causal story is built into the description that is the name's content [Stalnaker]
19. Language / C. Assigning Meanings / 10. Two-Dimensional Semantics
16430 Two-D says that a posteriori is primary and contingent, and the necessity is the secondary intension [Stalnaker]
16431 In one view, the secondary intension is metasemantic, about how the thinker relates to the content [Stalnaker]
25. Social Practice / F. Life Issues / 2. Euthanasia
4052 It has become normal to consider passive euthanasia while condemning active euthanasia [Rachels]
4053 If it is desirable that a given patient die, then moral objections to killing them do not apply [Rachels]