32 ideas
| 23657 | The existence of tensed verbs shows that not all truths are necessary truths [Reid] |
| 5750 | Consistency is modal, saying propositions are consistent if they could be true together [Melia] |
| 23655 | An ad hominem argument is good, if it is shown that the man's principles are inconsistent [Reid] |
| 5737 | Predicate logic has connectives, quantifiers, variables, predicates, equality, names and brackets [Melia] |
| 10163 | Propositional modal logic has been proved to be complete [Kripke, by Feferman/Feferman] |
| 5744 | First-order predicate calculus is extensional logic, but quantified modal logic is intensional (hence dubious) [Melia] |
| 10760 | With possible worlds, S4 and S5 are sound and complete, but S1-S3 are not even sound [Kripke, by Rossberg] |
| 16189 | The variable domain approach to quantified modal logic invalidates the Barcan Formula [Kripke, by Simchen] |
| 15132 | The Barcan formulas fail in models with varying domains [Kripke, by Williamson] |
| 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] |
| 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] |
| 23659 | If someone denies that he is thinking when he is conscious of it, we can only laugh [Reid] |
| 23662 | The existence of ideas is no more obvious than the existence of external objects [Reid] |
| 23661 | We are only aware of other beings through our senses; without that, we are alone in the universe [Reid] |
| 23654 | In obscure matters the few must lead the many, but the many usually lead in common sense [Reid] |
| 23660 | The theory of ideas, popular with philosophers, means past existence has to be proved [Reid] |
| 23658 | Consciousness is an indefinable and unique operation [Reid] |
| 23656 | The structure of languages reveals a uniformity in basic human opinions [Reid] |
| 23653 | If you can't distinguish the features of a complex object, your notion of it would be a muddle [Reid] |
| 5748 | We accept unverifiable propositions because of simplicity, utility, explanation and plausibility [Melia] |
| 23663 | There are axioms of taste - such as a general consensus about a beautiful face [Reid] |