27 ideas
21336 | Crates lived in poverty, and treated his whole life as a joke [Crates of Thebes, by Plutarch] |
1767 | Everyone should study philosophy until they see all people in the same light [Crates of Thebes, by Diog. Laertius] |
7798 | There are three axiom schemas for propositional logic [Girle] |
7786 | Propositional logic handles negation, disjunction, conjunction; predicate logic adds quantifiers, predicates, relations [Girle] |
7799 | Proposition logic has definitions for its three operators: or, and, and identical [Girle] |
7797 | Axiom systems of logic contain axioms, inference rules, and definitions of proof and theorems [Girle] |
7794 | There are seven modalities in S4, each with its negation [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] |
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] |
7789 | Necessary implication is called 'strict implication'; if successful, it is called 'entailment' [Girle] |
7790 | If an argument is invalid, a truth tree will indicate a counter-example [Girle] |
15200 | How could change consist of a conjunction of changeless facts? [McTaggart, by Le Poidevin] |
14761 | Change is not just having two different qualities at different points in some series [McTaggart] |
7800 | Analytic truths are divided into logically and conceptually necessary [Girle] |
7801 | Possibilities can be logical, theoretical, physical, economic or human [Girle] |
7792 | A world has 'access' to a world it generates, which is important in possible worlds semantics [Girle] |
2608 | For McTaggart time is seen either as fixed, or as relative to events [McTaggart, by Ayer] |
22936 | A-series time positions are contradictory, and yet all events occupy all of them! [McTaggart, by Le Poidevin] |
4231 | Time involves change, only the A-series explains change, but it involves contradictions, so time is unreal [McTaggart, by Lowe] |
8591 | There could be no time if nothing changed [McTaggart] |
22935 | The B-series can be inferred from the A-series, but not the other way round [McTaggart, by Le Poidevin] |
7802 | A-series uses past, present and future; B-series uses 'before' and 'after' [McTaggart, by Girle] |
4230 | A-series expressions place things in time, and their truth varies; B-series is relative, and always true [McTaggart, by Lowe] |
15199 | The B-series must depend on the A-series, because change must be explained [McTaggart, by Le Poidevin] |