Combining Philosophers

All the ideas for Anaxarchus, Jonathan Wolff and Robert S. Wolf

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52 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]
13. Knowledge Criteria / D. Scepticism / 1. Scepticism
Anaxarchus said that he was not even sure that he knew nothing [Anaxarchus, by Diog. Laertius]
24. Political Theory / A. Basis of a State / 1. A People / b. The natural life
Human beings can never really flourish in a long-term state of nature [Wolff,J]
24. Political Theory / A. Basis of a State / 1. A People / c. A unified people
Collective rationality is individuals doing their best, assuming others all do the same [Wolff,J]
Should love be the first virtue of a society, as it is of the family? [Wolff,J]
24. Political Theory / B. Nature of a State / 2. State Legitimacy / c. Social contract
For utilitarians, consent to the state is irrelevant, if it produces more happiness [Wolff,J]
Social contract theory has the attracton of including everyone, and being voluntary [Wolff,J]
Maybe voting in elections is a grant of legitimacy to the winners [Wolff,J]
24. Political Theory / B. Nature of a State / 2. State Legitimacy / d. General will
We can see the 'general will' as what is in the general interest [Wolff,J]
24. Political Theory / C. Ruling a State / 2. Leaders / c. Despotism
How can dictators advance the interests of the people, if they don't consult them about interests? [Wolff,J]
24. Political Theory / C. Ruling a State / 3. Government / a. Government
'Separation of powers' allows legislative, executive and judicial functions to monitor one another [Wolff,J]
24. Political Theory / D. Ideologies / 1. Ideology
Political choice can be by utility, or maximin, or maximax [Wolff,J]
24. Political Theory / D. Ideologies / 2. Anarchism
A realistic and less utopian anarchism looks increasingly like liberal democracy [Wolff,J]
It is hard for anarchists to deny that we need experts [Wolff,J]
24. Political Theory / D. Ideologies / 4. Social Utilitarianism
Utilitarianism probably implies a free market plus welfare [Wolff,J]
24. Political Theory / D. Ideologies / 5. Democracy / a. Nature of democracy
A system of democracy which includes both freedom and equality is almost impossible [Wolff,J]
Democracy expresses equal respect (which explains why criminals forfeit the vote) [Wolff,J]
Democracy has been seen as consistent with many types of inequality [Wolff,J]
A true democracy could not tolerate slavery, exploitation or colonialism [Wolff,J]
24. Political Theory / D. Ideologies / 5. Democracy / b. Consultation
We should decide whether voting is for self-interests, or for the common good [Wolff,J]
Condorcet proved that sensible voting leads to an emphatically right answer [Wolff,J]
24. Political Theory / D. Ideologies / 5. Democracy / e. Democratic minorities
Occasional defeat is acceptable, but a minority that is continually defeated is a problem [Wolff,J]
25. Social Practice / A. Freedoms / 4. Free market
Market prices indicate shortages and gluts, and where the profits are to be made [Wolff,J]
25. Social Practice / A. Freedoms / 5. Freedom of lifestyle
Liberty principles can't justify laws against duelling, incest between siblings and euthanasia [Wolff,J]
Either Difference allows unequal liberty, or Liberty makes implementing Difference impossible [Wolff,J]
25. Social Practice / B. Equalities / 1. Grounds of equality
Utilitarians argue for equal distribution because of diminishing utility of repetition [Wolff,J]
Difference Principle: all inequalities should be in favour of the disadvantaged [Wolff,J]
25. Social Practice / B. Equalities / 2. Political equality
Political equality is not much use without social equality [Wolff,J]
25. Social Practice / C. Rights / 1. Basis of Rights
Standard rights: life, free speech, assembly, movement, vote, stand (plus shelter, food, health?) [Wolff,J]
If natural rights are axiomatic, there is then no way we can defend them [Wolff,J]
If rights are natural, rather than inferred, how do we know which rights we have? [Wolff,J]
25. Social Practice / C. Rights / 4. Property rights
Utilitarians might say property ownership encourages the best use of the land [Wolff,J]
25. Social Practice / D. Justice / 1. Basis of justice
Rights and justice are only the last resorts of a society, something to fall back on [Wolff,J]
25. Social Practice / D. Justice / 2. The Law / d. Legal positivism
Following some laws is not a moral matter; trivial traffic rules, for example [Wolff,J]