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All the ideas for 'What is Logic?st1=Ian Hacking', 'Review: Meinong 'Untersuchungen zur..'' and 'Necessity and Non-Existence'

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30 ideas

1. Philosophy / F. Analytic Philosophy / 6. Logical Analysis
21546 We can't sharply distinguish variables, domains and values, if symbols frighten us [Russell]
2. Reason / D. Definition / 3. Types of Definition
13838 A decent modern definition should always imply a semantics [Hacking]
3. Truth / B. Truthmakers / 5. What Makes Truths / a. What makes truths
15063 Some sentences depend for their truth on worldly circumstances, and others do not [Fine,K]
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]
7. Existence / A. Nature of Existence / 2. Types of Existence
15078 There are levels of existence, as well as reality; objects exist at the lowest level in which they can function [Fine,K]
7. Existence / D. Theories of Reality / 3. Reality
15072 Bottom level facts are subject to time and world, middle to world but not time, and top to neither [Fine,K]
7. Existence / D. Theories of Reality / 8. Facts / b. Types of fact
15071 Tensed and tenseless sentences state two sorts of fact, which belong to two different 'realms' of reality [Fine,K]
9. Objects / A. Existence of Objects / 4. Impossible objects
21531 Common sense agrees with Meinong (rather than Russell) that 'Pegasus is a flying horse' is true [Lackey on Russell]
21545 I prefer to deny round squares, and deal with the difficulties by the theory of denoting [Russell]
9. Objects / B. Unity of Objects / 1. Unifying an Object / a. Intrinsic unification
15075 Modal features are not part of entities, because they are accounted for by the entity [Fine,K]
9. Objects / D. Essence of Objects / 6. Essence as Unifier
15065 What it is is fixed prior to existence or the object's worldly features [Fine,K]
9. Objects / D. Essence of Objects / 9. Essence and Properties
15076 Essential features of an object have no relation to how things actually are [Fine,K]
9. Objects / F. Identity among Objects / 5. Self-Identity
15073 Self-identity should have two components, its existence, and its neutral identity with itself [Fine,K]
9. Objects / F. Identity among Objects / 6. Identity between Objects
15074 We would understand identity between objects, even if their existence was impossible [Fine,K]
10. Modality / A. Necessity / 8. Transcendental Necessity
15064 Proper necessary truths hold whatever the circumstances; transcendent truths regardless of circumstances [Fine,K]
10. Modality / C. Sources of Modality / 6. Necessity from Essence
15070 It is the nature of Socrates to be a man, so necessarily he is a man [Fine,K]
10. Modality / E. Possible worlds / 2. Nature of Possible Worlds / a. Nature of possible worlds
15069 Possible worlds may be more limited, to how things might actually turn out [Fine,K]
15068 The actual world is a totality of facts, so we also think of possible worlds as totalities [Fine,K]
27. Natural Reality / D. Time / 2. Passage of Time / c. Tenses and time
15067 A-theorists tend to reject the tensed/tenseless distinction [Fine,K]
15077 It is said that in the A-theory, all existents and objects must be tensed, as well as the sentences [Fine,K]
27. Natural Reality / D. Time / 2. Passage of Time / f. Tenseless (B) series
15066 B-theorists say tensed sentences have an unfilled argument-place for a time [Fine,K]