Combining Philosophers

All the ideas for Douglas Lackey, Rod Girle and Max Black

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21 ideas

4. Formal Logic / B. Propositional Logic PL / 1. Propositional Logic
7798 There are three axiom schemas for propositional logic [Girle]
7786 Propositional logic handles negation, disjunction, conjunction; predicate logic adds quantifiers, predicates, relations [Girle]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / a. Symbols of PL
7799 Proposition logic has definitions for its three operators: or, and, and identical [Girle]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / e. Axioms of PL
7797 Axiom systems of logic contain axioms, inference rules, and definitions of proof and theorems [Girle]
4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / g. System S4
7794 There are seven modalities in S4, each with its negation [Girle]
4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5
7793 ◊p → □◊p is the hallmark of S5 [Girle]
7795 S5 has just six modalities, and all strings can be reduced to those [Girle]
4. Formal Logic / D. Modal Logic ML / 4. Alethic Modal Logic
7787 Possible worlds logics use true-in-a-world rather than true [Girle]
7796 Modal logics were studied in terms of axioms, but now possible worlds semantics is added [Girle]
7788 Modal logic has four basic modal negation equivalences [Girle]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / j. Axiom of Choice IX
10196 The Axiom of Choice needs a criterion of choice [Black]
5. Theory of Logic / B. Logical Consequence / 7. Strict Implication
7789 Necessary implication is called 'strict implication'; if successful, it is called 'entailment' [Girle]
5. Theory of Logic / H. Proof Systems / 5. Tableau Proof
7790 If an argument is invalid, a truth tree will indicate a counter-example [Girle]
5. Theory of Logic / L. Paradox / 5. Paradoxes in Set Theory / b. Cantor's paradox
21554 Sets always exceed terms, so all the sets must exceed all the sets [Lackey]
5. Theory of Logic / L. Paradox / 5. Paradoxes in Set Theory / c. Burali-Forti's paradox
21553 It seems that the ordinal number of all the ordinals must be bigger than itself [Lackey]
9. Objects / A. Existence of Objects / 5. Individuation / b. Individuation by properties
10194 Two things can only be distinguished by a distinct property or a distinct relation [Black]
9. Objects / F. Identity among Objects / 5. Self-Identity
10193 The 'property' of self-identity is uselessly tautological [Black]
9. Objects / F. Identity among Objects / 7. Indiscernible Objects
10195 If the universe just held two indiscernibles spheres, that refutes the Identity of Indiscernibles [Black]
10. Modality / A. Necessity / 3. Types of Necessity
7800 Analytic truths are divided into logically and conceptually necessary [Girle]
10. Modality / B. Possibility / 1. Possibility
7801 Possibilities can be logical, theoretical, physical, economic or human [Girle]
10. Modality / E. Possible worlds / 1. Possible Worlds / a. Possible worlds
7792 A world has 'access' to a world it generates, which is important in possible worlds semantics [Girle]