68 ideas
| 11832 | We learn a concept's relations by using it, without reducing it to anything [Wiggins] |
| 15413 | With four tense operators, all complex tenses reduce to fourteen basic cases [Burgess] |
| 15415 | The temporal Barcan formulas fix what exists, which seems absurd [Burgess] |
| 15430 | Is classical logic a part of intuitionist logic, or vice versa? [Burgess] |
| 15431 | It is still unsettled whether standard intuitionist logic is complete [Burgess] |
| 15429 | Relevance logic's → is perhaps expressible by 'if A, then B, for that reason' [Burgess] |
| 15404 | Technical people see logic as any formal system that can be studied, not a study of argument validity [Burgess] |
| 15405 | Classical logic neglects the non-mathematical, such as temporality or modality [Burgess] |
| 15421 | Classical logic neglects counterfactuals, temporality and modality, because maths doesn't use them [Burgess] |
| 15427 | The Cut Rule expresses the classical idea that entailment is transitive [Burgess] |
| 15403 | Philosophical logic is a branch of logic, and is now centred in computer science [Burgess] |
| 15407 | Formalising arguments favours lots of connectives; proving things favours having very few [Burgess] |
| 15424 | Asserting a disjunction from one disjunct seems odd, but can be sensible, and needed in maths [Burgess] |
| 15409 | All occurrences of variables in atomic formulas are free [Burgess] |
| 15414 | The denotation of a definite description is flexible, rather than rigid [Burgess] |
| 11863 | (λx)[Man x] means 'the property x has iff x is a man'. [Wiggins] |
| 15406 | 'Induction' and 'recursion' on complexity prove by connecting a formula to its atomic components [Burgess] |
| 15426 | We can build one expanding sequence, instead of a chain of deductions [Burgess] |
| 15425 | The sequent calculus makes it possible to have proof without transitivity of entailment [Burgess] |
| 15408 | 'Tautologies' are valid formulas of classical sentential logic - or substitution instances in other logics [Burgess] |
| 15418 | Validity (for truth) and demonstrability (for proof) have correlates in satisfiability and consistency [Burgess] |
| 15411 | We only need to study mathematical models, since all other models are isomorphic to these [Burgess] |
| 15412 | Models leave out meaning, and just focus on truth values [Burgess] |
| 15416 | We aim to get the technical notion of truth in all models matching intuitive truth in all instances [Burgess] |
| 15428 | The Liar seems like a truth-value 'gap', but dialethists see it as a 'glut' [Burgess] |
| 14746 | What exists can't depend on our conceptual scheme, and using all conceptual schemes is too liberal [Sider on Wiggins] |
| 11900 | We can accept criteria of distinctness and persistence, without making the counterfactual claims [Mackie,P on Wiggins] |
| 11870 | Activity individuates natural things, functions do artefacts, and intentions do artworks [Wiggins] |
| 11866 | The idea of 'thisness' is better expressed with designation/predication and particular/universal [Wiggins] |
| 11896 | A sortal essence is a thing's principle of individuation [Wiggins, by Mackie,P] |
| 15835 | Wiggins's sortal essentialism rests on a thing's principle of individuation [Wiggins, by Mackie,P] |
| 11841 | The evening star is the same planet but not the same star as the morning star, since it is not a star [Wiggins] |
| 10679 | 'Sortalism' says parts only compose a whole if it falls under a sort or kind [Wiggins, by Hossack] |
| 14363 | Identity a=b is only possible with some concept to give persistence and existence conditions [Wiggins, by Strawson,P] |
| 14364 | A thing is necessarily its highest sortal kind, which entails an essential constitution [Wiggins, by Strawson,P] |
| 11851 | Many predicates are purely generic, or pure determiners, rather than sortals [Wiggins] |
| 11865 | The possibility of a property needs an essential sortal concept to conceive it [Wiggins] |
| 14744 | Objects can only coincide if they are of different kinds; trees can't coincide with other trees [Wiggins, by Sider] |
| 11852 | Is the Pope's crown one crown, if it is made of many crowns? [Wiggins] |
| 11875 | Boundaries are not crucial to mountains, so they are determinate without a determinate extent [Wiggins] |
| 14749 | Identity is an atemporal relation, but composition is relative to times [Wiggins, by Sider] |
| 11844 | If I destroy an item, I do not destroy each part of it [Wiggins] |
| 11861 | We can forget about individual or particularized essences [Wiggins] |
| 11871 | Essences are not explanations, but individuations [Wiggins] |
| 11879 | Essentialism is best represented as a predicate-modifier: □(a exists → a is F) [Wiggins, by Mackie,P] |
| 11835 | The nominal essence is the idea behind a name used for sorting [Wiggins] |
| 11876 | It is easier to go from horses to horse-stages than from horse-stages to horses [Wiggins] |
| 11858 | The question is not what gets the title 'Theseus' Ship', but what is identical with the original [Wiggins] |
| 11843 | Identity over a time and at a time aren't different concepts [Wiggins] |
| 11864 | Hesperus=Hesperus, and Phosphorus=Hesperus, so necessarily Phosphorus=Hesperus [Wiggins] |
| 11831 | The formal properties of identity are reflexivity and Leibniz's Law [Wiggins] |
| 14362 | Relative Identity is incompatible with the Indiscernibility of Identicals [Wiggins, by Strawson,P] |
| 11838 | Relativity of Identity makes identity entirely depend on a category [Wiggins] |
| 11847 | To identify two items, we must have a common sort for them [Wiggins] |
| 11839 | Do both 'same f as' and '=' support Leibniz's Law? [Wiggins] |
| 11845 | Substitutivity, and hence most reasoning, needs Leibniz's Law [Wiggins] |
| 15420 | De re modality seems to apply to objects a concept intended for sentences [Burgess] |
| 15417 | Logical necessity has two sides - validity and demonstrability - which coincide in classical logic [Burgess] |
| 15419 | General consensus is S5 for logical modality of validity, and S4 for proof [Burgess] |
| 15423 | It is doubtful whether the negation of a conditional has any clear meaning [Burgess] |
| 15422 | Three conditionals theories: Materialism (material conditional), Idealism (true=assertable), Nihilism (no truth) [Burgess] |
| 11869 | Possible worlds rest on the objects about which we have suppositions [Wiggins] |
| 11850 | Not every story corresponds to a possible world [Wiggins] |
| 11848 | Asking 'what is it?' nicely points us to the persistence of a continuing entity [Wiggins] |
| 7272 | Maybe lots of qualia lead to intentionality, rather than intentionality being basic [Gildersleve] |
| 11859 | The mind conceptualizes objects; yet objects impinge upon the mind [Wiggins] |
| 11836 | We can use 'concept' for the reference, and 'conception' for sense [Wiggins] |
| 11860 | Lawlike propensities are enough to individuate natural kinds [Wiggins] |