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All the ideas for 'What is Logic?st1=Ian Hacking', 'Contrib to Critique of Hegel's Phil of Right' and 'Transworld Identity or worldbound Individuals?'

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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
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]
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 / E. Possible worlds / 1. Possible Worlds / a. Possible worlds
11984 Asserting a possible property is to say it would have had the property if that world had been actual [Plantinga]
10. Modality / E. Possible worlds / 2. Nature of Possible Worlds / a. Nature of possible worlds
11980 A possible world is a maximal possible state of affairs [Plantinga]
10. Modality / E. Possible worlds / 3. Transworld Objects / a. Transworld identity
11982 If possible Socrates differs from actual Socrates, the Indiscernibility of Identicals says they are different [Plantinga]
11983 It doesn't matter that we can't identify the possible Socrates; we can't identify adults from baby photos [Plantinga]
11985 If individuals can only exist in one world, then they can never lack any of their properties [Plantinga]
10. Modality / E. Possible worlds / 3. Transworld Objects / c. Counterparts
11986 The counterparts of Socrates have self-identity, but only the actual Socrates has identity-with-Socrates [Plantinga]
11987 Counterpart Theory absurdly says I would be someone else if things went differently [Plantinga]
24. Political Theory / C. Ruling a State / 4. Changing the State / c. Revolution
21991 The middle class gain freedom through property, but workers can only free all of humanity [Marx, by Singer]
21990 Theory is as much a part of a revolution as material force is [Marx]
29. Religion / D. Religious Issues / 1. Religious Commitment / a. Religious Belief
7128 Religion is the opium of the people, and real happiness requires its abolition [Marx]