31 ideas
| 5750 | Consistency is modal, saying propositions are consistent if they could be true together [Melia] |
| 192 | Only one thing can be contrary to something [Plato] |
| 5737 | Predicate logic has connectives, quantifiers, variables, predicates, equality, names and brackets [Melia] |
| 5744 | First-order predicate calculus is extensional logic, but quantified modal logic is intensional (hence dubious) [Melia] |
| 5740 | Second-order logic needs second-order variables and quantification into predicate position [Melia] |
| 5741 | If every model that makes premises true also makes conclusion true, the argument is valid [Melia] |
| 5735 | Maybe names and predicates can capture any fact [Melia] |
| 5736 | No sort of plain language or levels of logic can express modal facts properly [Melia] |
| 190 | If asked whether justice itself is just or unjust, you would have to say that it is just [Plato] |
| 5746 | The Identity of Indiscernibles is contentious for qualities, and trivial for non-qualities [Melia] |
| 5738 | We may be sure that P is necessary, but is it necessarily necessary? [Melia] |
| 5732 | 'De re' modality is about things themselves, 'de dicto' modality is about propositions [Melia] |
| 5739 | Sometimes we want to specify in what ways a thing is possible [Melia] |
| 5734 | Possible worlds make it possible to define necessity and counterfactuals without new primitives [Melia] |
| 5742 | In possible worlds semantics the modal operators are treated as quantifiers [Melia] |
| 5743 | If possible worlds semantics is not realist about possible worlds, logic becomes merely formal [Melia] |
| 5749 | Possible worlds could be real as mathematics, propositions, properties, or like books [Melia] |
| 5751 | The truth of propositions at possible worlds are implied by the world, just as in books [Melia] |
| 20184 | The only real evil is loss of knowledge [Plato] |
| 20185 | The most important things in life are wisdom and knowledge [Plato] |
| 22200 | If you eliminate the impossible, the truth will remain, even if it is weird [Conan Doyle] |
| 191 | Everything resembles everything else up to a point [Plato] |
| 5748 | We accept unverifiable propositions because of simplicity, utility, explanation and plausibility [Melia] |
| 203 | Courage is knowing what should or shouldn't be feared [Plato] |
| 202 | No one willingly and knowingly embraces evil [Plato] |
| 193 | Some things are good even though they are not beneficial to men [Plato] |
| 197 | Some pleasures are not good, and some pains are not evil [Plato] |
| 200 | People tend only to disapprove of pleasure if it leads to pain, or prevents future pleasure [Plato] |
| 188 | Socrates did not believe that virtue could be taught [Plato] |
| 204 | Socrates is contradicting himself in claiming virtue can't be taught, but that it is knowledge [Plato] |
| 189 | If we punish wrong-doers, it shows that we believe virtue can be taught [Plato] |