Combining Texts

All the ideas for 'Notebooks 1914-1916', 'A Realistic Theory of Categories' and 'A Tour through Mathematical Logic'

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29 ideas

1. Philosophy / F. Analytic Philosophy / 5. Linguistic Analysis
18274 Analysis complicates a statement, but only as far as the complexity of its meaning [Wittgenstein]
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 ∀
13522 Universal Generalization: If we prove P(x) with no special assumptions, we can conclude ∀xP(x) [Wolf,RS]
13521 Universal Specification: ∀xP(x) implies P(t). True for all? Then true for an instance [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 / 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 / 1. Overview of Logic
16908 We can dispense with self-evidence, if language itself prevents logical mistakes [Jeshion on Wittgenstein]
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 / E. Structures of Logic / 1. Logical Form
18276 A statement's logical form derives entirely from its constituents [Wittgenstein]
5. Theory of Logic / E. Structures of Logic / 2. Logical Connectives / a. Logical connectives
6563 'And' and 'not' are non-referring terms, which do not represent anything [Wittgenstein, by Fogelin]
5. Theory of Logic / J. Model Theory in Logic / 1. Logical Models
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]
13519 Model theory uses sets to show that mathematical deduction fits mathematical truth [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 / C. Structure of Existence / 6. Fundamentals / d. Logical atoms
23472 The sense of propositions relies on the world's basic logical structure [Wittgenstein]
7. Existence / E. Categories / 3. Proposed Categories
13120 Chisholm divides things into contingent and necessary, and then individuals, states and non-states [Chisholm, by Westerhoff]
12. Knowledge Sources / A. A Priori Knowledge / 5. A Priori Synthetic
23500 My main problem is the order of the world, and whether it is knowable a priori [Wittgenstein]
16. Persons / B. Nature of the Self / 4. Presupposition of Self
22323 The philosophical I is the metaphysical subject, the limit - not a part of the world [Wittgenstein]
19. Language / A. Nature of Meaning / 2. Meaning as Mental
23481 Propositions assemble a world experimentally, like the model of a road accident [Wittgenstein]
25. Social Practice / F. Life Issues / 4. Suicide
4678 Absolute prohibitions are the essence of ethics, and suicide is the most obvious example [Wittgenstein]