Ideas of Robert S. Wolf, by Theme
[American, fl. 2005, Teaches mathematics at California Polytechnic State University.]
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4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / b. Terminology of PL
13520

A 'tautology' must include connectives

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

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)

13521

Universal Specification: ∀xP(x) implies P(t). True for all? Then true for an instance

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

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

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

5. Theory of Logic / A. Overview of Logic / 5. FirstOrder Logic
13534

In firstorder logic syntactic and semantic consequence ( and =) nicely coincide

13535

Firstorder logic is weakly complete (valid sentences are provable); we can't prove every sentence or its negation

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

13531

Model theory reveals the structures of mathematics

13532

Model theory 'structures' have a 'universe', some 'relations', some 'functions', and some 'constants'

13533

Firstorder model theory rests on completeness, compactness, and the LöwenheimSkolemTarski theorem

5. Theory of Logic / J. Model Theory in Logic / 2. Isomorphisms
13537

An 'isomorphism' is a bijection that preserves all structural components

5. Theory of Logic / J. Model Theory in Logic / 3. LöwenheimSkolem Theorems
13539

The LST Theorem is a serious limitation of firstorder logic

5. Theory of Logic / K. Features of Logics / 4. Completeness
13538

If a theory is complete, only a more powerful language can strengthen it

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

6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / e. Ordinal numbers
13530

An ordinal is an equivalence class of wellorderings, or a transitive set whose members are transitive

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
