34 ideas
| 7786 | Propositional logic handles negation, disjunction, conjunction; predicate logic adds quantifiers, predicates, relations [Girle] |
| 7798 | There are three axiom schemas for propositional logic [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] |
| 7788 | Modal logic has four basic modal negation equivalences [Girle] |
| 7796 | Modal logics were studied in terms of axioms, but now possible worlds semantics is added [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] |
| 21315 | A tree remains the same in the popular sense, but not in the strict philosophical sense [Butler] |
| 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] |
| 6685 | 'Subjectivism' is an extension of relativism from the social group to the individual [Graham] |
| 21317 | Despite consciousness fluctuating, we are aware that it belongs to one person [Butler] |
| 21313 | If consciousness of events makes our identity, then if we have forgotten them we didn't exist then [Butler] |
| 21314 | Consciousness presupposes personal identity, so it cannot constitute it [Butler] |
| 21318 | If the self changes, we have no responsibilities, and no interest in past or future [Butler] |
| 6699 | The chain of consequences may not be the same as the chain of responsibility [Graham] |
| 6698 | Negative consequences are very hard (and possibly impossible) to assess [Graham] |
| 6700 | We can't criticise people because of unforeseeable consequences [Graham] |
| 6704 | Egoism submits to desires, but cannot help form them [Graham] |
| 6701 | Rescue operations need spontaneous benevolence, not careful thought [Graham] |
| 6693 | 'What if everybody did that?' rather misses the point as an objection to cheating [Graham] |
| 6691 | It is more plausible to say people can choose between values, than that they can create them [Graham] |
| 6688 | Life is only absurd if you expected an explanation and none turns up [Graham] |
| 6705 | Existentialism may transcend our nature, unlike eudaimonism [Graham] |
| 6690 | A standard problem for existentialism is the 'sincere Nazi' [Graham] |
| 6689 | The key to existentialism: the way you make choices is more important than what you choose [Graham] |
| 6706 | The great religions are much more concerned with the religious life than with ethics [Graham] |
| 6709 | Western religion saves us from death; Eastern religion saves us from immortality [Graham] |