### Ideas from 'Modal Logics and Philosophy' by Rod Girle [2000], by Theme Structure

#### [found in 'Modal Logics and Philosophy' by Girle,Rod [Acumen 2000,1-902683-15-3]].

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###### 4. Formal Logic / B. Propositional Logic PL / 1. Propositional Logic
 7798 There are three axiom schemas for propositional logic
 7786 Propositional logic handles negation, disjunction, conjunction; predicate logic adds quantifiers, predicates, relations
###### 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
###### 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
###### 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
###### 4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5
 7793 ◊p → □◊p is the hallmark of S5
 7791 The simplest of the logics based on possible worlds is Lewis's S5
 7795 S5 has just six modalities, and all strings can be reduced to those
###### 4. Formal Logic / D. Modal Logic ML / 4. Alethic Modal Logic
 7787 Possible worlds logics use true-in-a-world rather than true
 7788 Modal logic has four basic modal negation equivalences
 7796 Modal logics were studied in terms of axioms, but now possible worlds semantics is added
###### 5. Theory of Logic / B. Logical Consequence / 7. Strict Implication
 7789 Necessary implication is called 'strict implication'; if successful, it is called 'entailment'
###### 5. Theory of Logic / H. Proof Systems / 5. Tableau Proof
 7790 If an argument is invalid, a truth tree will indicate a counter-example
###### 10. Modality / A. Necessity / 3. Types of Necessity
 7800 Analytic truths are divided into logically and conceptually necessary
###### 10. Modality / B. Possibility / 1. Possibility
 7801 Possibilities can be logical, theoretical, physical, economic or human
###### 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