Combining Philosophers

All the ideas for Thrasymachus, Rod Girle and C.I. Lewis

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31 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
7791 The simplest of the logics based on possible worlds is Lewis's S5 [Lewis,CI, by Girle]
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]
5. Theory of Logic / A. Overview of Logic / 1. Overview of Logic
9358 There are several logics, none of which will ever derive falsehoods from truth [Lewis,CI]
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 / D. Assumptions for Logic / 2. Excluded Middle
9357 Excluded middle is just our preference for a simplified dichotomy in experience [Lewis,CI]
5. Theory of Logic / F. Referring in Logic / 1. Naming / a. Names
9364 Names represent a uniformity in experience, or they name nothing [Lewis,CI]
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]
10. Modality / A. Necessity / 2. Nature of Necessity
11002 Equating necessity with informal provability is the S4 conception of necessity [Lewis,CI, by Read]
10. Modality / A. Necessity / 3. Types of Necessity
7800 Analytic truths are divided into logically and conceptually necessary [Girle]
10. Modality / A. Necessity / 11. Denial of Necessity
9362 Necessary truths are those we will maintain no matter what [Lewis,CI]
10. Modality / B. Possibility / 1. Possibility
7801 Possibilities can be logical, theoretical, physical, economic or human [Girle]
10. Modality / B. Possibility / 8. Conditionals / a. Conditionals
7803 Modal logic began with translation difficulties for 'If...then' [Lewis,CI, by 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]
12. Knowledge Sources / A. A Priori Knowledge / 7. A Priori from Convention
9365 We can maintain a priori principles come what may, but we can also change them [Lewis,CI]
12. Knowledge Sources / E. Direct Knowledge / 4. Memory
21500 We rely on memory for empirical beliefs because they mutually support one another [Lewis,CI]
21501 If we doubt memories we cannot assess our doubt, or what is being doubted [Lewis,CI]
13. Knowledge Criteria / B. Internal Justification / 4. Foundationalism / a. Foundationalism
6556 If anything is to be probable, then something must be certain [Lewis,CI]
13. Knowledge Criteria / B. Internal Justification / 5. Coherentism / b. Pro-coherentism
21498 Congruents assertions increase the probability of each individual assertion in the set [Lewis,CI]
18. Thought / C. Content / 8. Intension
5828 Extension is the class of things, intension is the correct definition of the thing, and intension determines extension [Lewis,CI]
18. Thought / E. Abstraction / 2. Abstracta by Selection
9361 We have to separate the mathematical from physical phenomena by abstraction [Lewis,CI]
26. Natural Theory / D. Laws of Nature / 8. Scientific Essentialism / a. Scientific essentialism
9363 Science seeks classification which will discover laws, essences, and predictions [Lewis,CI]
28. God / C. Attitudes to God / 3. Deism
1558 Clearly the gods ignore human affairs, or they would have given us justice [Thrasymachus]