Combining Texts

All the ideas for 'fragments/reports', 'Shame and Necessity' and 'A Tour through Mathematical Logic'

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31 ideas

4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / b. Terminology of PL
A 'tautology' must include connectives [Wolf,RS]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / c. Derivation rules of PL
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 ∀
Universal Generalization: If we prove P(x) with no special assumptions, we can conclude ∀xP(x) [Wolf,RS]
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 ∃
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
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
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
In first-order logic syntactic and semantic consequence (|- and |=) nicely coincide [Wolf,RS]
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 / J. Model Theory in Logic / 1. Logical Models
Model theory reveals the structures of mathematics [Wolf,RS]
Model theory 'structures' have a 'universe', some 'relations', some 'functions', and some 'constants' [Wolf,RS]
Model theory uses sets to show that mathematical deduction fits mathematical truth [Wolf,RS]
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
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
The LST Theorem is a serious limitation of first-order logic [Wolf,RS]
5. Theory of Logic / K. Features of Logics / 4. Completeness
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
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
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
Modern mathematics has unified all of its objects within set theory [Wolf,RS]
16. Persons / F. Free Will / 5. Against Free Will
It is an absurd Kantian idea that at the limit rationality and freedom coincide [Williams,B]
There is only a problem of free will if you think the notion of 'voluntary' can be metaphysically deepened [Williams,B]
20. Action / B. Preliminaries of Action / 2. Willed Action / d. Weakness of will
We judge weakness of will by an assessment after the event is concluded [Williams,B, by Cottingham]
20. Action / C. Motives for Action / 4. Responsibility for Actions
Responsibility involves cause, intention, state of mind, and response after the event [Williams,B]
22. Metaethics / A. Ethics Foundations / 1. Nature of Ethics / g. Moral responsibility
In bad actions, guilt points towards victims, and shame to the agent [Williams,B]
23. Ethics / C. Virtue Theory / 1. Virtue Theory / a. Nature of virtue
Greek moral progress came when 'virtue' was freed from social status [Williams,B]
23. Ethics / D. Deontological Ethics / 2. Duty
The modern idea of duty is unknown in archaic Greece [Williams,B]
23. Ethics / D. Deontological Ethics / 6. Motivation for Duty
If the moral self is seen as characterless, then other people have a very limited role in our moral lives [Williams,B]
If reason cannot lead people to good, we must hope they have an internal voice [Williams,B]
25. Social Practice / E. Policies / 5. Education / b. Education principles
Learned men gain more in one day than others do in a lifetime [Posidonius]
27. Natural Reality / D. Time / 1. Nature of Time / d. Time as measure
Time is an interval of motion, or the measure of speed [Posidonius, by Stobaeus]
29. Religion / D. Religious Issues / 3. Problem of Evil / a. Problem of Evil
There is a problem of evil only if you expect the world to be good [Williams,B]