Combining Texts

All the ideas for 'Set Theory and related topics (2nd ed)', 'Reference and Essence (1st edn)' and 'Higher-Order Logic'

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19 ideas

2. Reason / D. Definition / 11. Ostensive Definition
18889 Ostensive definitions needn't involve pointing, but must refer to something specific [Salmon,N]
4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5
14627 S4, and therefore S5, are invalid for metaphysical modality [Salmon,N, by Williamson]
4. Formal Logic / F. Set Theory ST / 3. Types of Set / e. Equivalence classes
8920 Equivalence relations are reflexive, symmetric and transitive, and classify similar objects [Lipschutz]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / j. Axiom of Choice IX
10301 The axiom of choice is controversial, but it could be replaced [Shapiro]
5. Theory of Logic / A. Overview of Logic / 5. First-Order Logic
10588 First-order logic is Complete, and Compact, with the Löwenheim-Skolem Theorems [Shapiro]
5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic
10298 Some say that second-order logic is mathematics, not logic [Shapiro]
10299 If the aim of logic is to codify inferences, second-order logic is useless [Shapiro]
5. Theory of Logic / B. Logical Consequence / 1. Logical Consequence
10300 Logical consequence can be defined in terms of the logical terminology [Shapiro]
5. Theory of Logic / G. Quantification / 5. Second-Order Quantification
10290 Second-order variables also range over properties, sets, relations or functions [Shapiro]
5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems
10590 Up Löwenheim-Skolem: if natural numbers satisfy wffs, then an infinite domain satisfies them [Shapiro]
10296 The Löwenheim-Skolem Theorems fail for second-order languages with standard semantics [Shapiro]
10297 The Löwenheim-Skolem theorem seems to be a defect of first-order logic [Shapiro]
10292 Downward Löwenheim-Skolem: if there's an infinite model, there is a countable model [Shapiro]
6. Mathematics / B. Foundations for Mathematics / 4. Axioms for Number / e. Peano arithmetic 2nd-order
10294 Second-order logic has the expressive power for mathematics, but an unworkable model theory [Shapiro]
8. Modes of Existence / B. Properties / 11. Properties as Sets
10591 Logicians use 'property' and 'set' interchangeably, with little hanging on it [Shapiro]
9. Objects / D. Essence of Objects / 7. Essence and Necessity / a. Essence as necessary properties
18888 Essentialism says some properties must be possessed, if a thing is to exist [Salmon,N]
19. Language / B. Reference / 1. Reference theories
18886 Frege's 'sense' solves four tricky puzzles [Salmon,N]
19. Language / B. Reference / 3. Direct Reference / a. Direct reference
18887 The perfect case of direct reference is a variable which has been assigned a value [Salmon,N]
26. Natural Theory / B. Natural Kinds / 5. Reference to Natural Kinds
18891 Nothing in the direct theory of reference blocks anti-essentialism; water structure might have been different [Salmon,N]