Combining Texts

All the ideas for 'Existence and Quantification', 'Metaphysics' and 'A Tour through Mathematical Logic'

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30 ideas

4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / b. Terminology of PL
13520 A 'tautology' must include connectives [Wolf,RS]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / c. Derivation rules of PL
13524 Deduction Theorem: T∪{P}|-Q, then T|-(P→Q), which justifies Conditional Proof [Wolf,RS]
4. Formal Logic / C. Predicate Calculus PC / 2. Tools of Predicate Calculus / d. Universal quantifier ∀
13521 Universal Specification: ∀xP(x) implies P(t). True for all? Then true for an instance [Wolf,RS]
13522 Universal Generalization: If we prove P(x) with no special assumptions, we can conclude ∀xP(x) [Wolf,RS]
4. Formal Logic / C. Predicate Calculus PC / 2. Tools of Predicate Calculus / e. Existential quantifier ∃
13523 Existential Generalization (or 'proof by example'): if we can say P(t), then we can say something is P [Wolf,RS]
4. Formal Logic / D. Modal Logic ML / 1. Modal Logic
5745 Quine says quantified modal logic creates nonsense, bad ontology, and false essentialism [Melia on Quine]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / e. Axiom of the Empty Set IV
13529 Empty Set: ∃x∀y ¬(y∈x). The unique empty set exists [Wolf,RS]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / n. Axiom of Comprehension
13526 Comprehension Axiom: if a collection is clearly specified, it is a set [Wolf,RS]
5. Theory of Logic / A. Overview of Logic / 5. First-Order Logic
13534 In first-order logic syntactic and semantic consequence (|- and |=) nicely coincide [Wolf,RS]
13535 First-order logic is weakly complete (valid sentences are provable); we can't prove every sentence or its negation [Wolf,RS]
5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic
8789 Various strategies try to deal with the ontological commitments of second-order logic [Hale/Wright on Quine]
5. Theory of Logic / J. Model Theory in Logic / 1. Logical Models
13519 Model theory uses sets to show that mathematical deduction fits mathematical truth [Wolf,RS]
13531 Model theory reveals the structures of mathematics [Wolf,RS]
13532 Model theory 'structures' have a 'universe', some 'relations', some 'functions', and some 'constants' [Wolf,RS]
13533 First-order model theory rests on completeness, compactness, and the Löwenheim-Skolem-Tarski theorem [Wolf,RS]
5. Theory of Logic / J. Model Theory in Logic / 2. Isomorphisms
13537 An 'isomorphism' is a bijection that preserves all structural components [Wolf,RS]
5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems
13539 The LST Theorem is a serious limitation of first-order logic [Wolf,RS]
5. Theory of Logic / K. Features of Logics / 4. Completeness
13538 If a theory is complete, only a more powerful language can strengthen it [Wolf,RS]
5. Theory of Logic / K. Features of Logics / 10. Monotonicity
13525 Most deductive logic (unlike ordinary reasoning) is 'monotonic' - we don't retract after new givens [Wolf,RS]
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / e. Ordinal numbers
13530 An ordinal is an equivalence class of well-orderings, or a transitive set whose members are transitive [Wolf,RS]
6. Mathematics / B. Foundations for Mathematics / 6. Mathematics as Set Theory / a. Mathematics is set theory
13518 Modern mathematics has unified all of its objects within set theory [Wolf,RS]
7. Existence / A. Nature of Existence / 3. Being / b. Being and existence
16966 Philosophers tend to distinguish broad 'being' from narrower 'existence' - but I reject that [Quine]
7. Existence / A. Nature of Existence / 6. Criterion for Existence
16965 All we have of general existence is what existential quantifiers express [Quine]
7. Existence / C. Structure of Existence / 8. Stuff / a. Pure stuff
16771 A composite is a true unity if all of its parts fall under one essence [Scheibler]
7. Existence / D. Theories of Reality / 11. Ontological Commitment / b. Commitment of quantifiers
16963 Existence is implied by the quantifiers, not by the constants [Quine]
7. Existence / D. Theories of Reality / 11. Ontological Commitment / c. Commitment of predicates
16964 Theories are committed to objects of which some of its predicates must be true [Quine]
7. Existence / D. Theories of Reality / 11. Ontological Commitment / d. Commitment of theories
4216 Express a theory in first-order predicate logic; its ontology is the types of bound variable needed for truth [Quine, by Lowe]
18966 Ontological commitment of theories only arise if they are classically quantified [Quine]
7. Existence / D. Theories of Reality / 11. Ontological Commitment / e. Ontological commitment problems
14490 You can be implicitly committed to something without quantifying over it [Thomasson on Quine]
7. Existence / E. Categories / 1. Categories
16961 In formal terms, a category is the range of some style of variables [Quine]