72 ideas
| 15357 | Philosophy is the most general intellectual discipline [Horsten] |
| 15352 | A definition should allow the defined term to be eliminated [Horsten] |
| 15324 | Semantic theories of truth seek models; axiomatic (syntactic) theories seek logical principles [Horsten] |
| 15323 | Truth is a property, because the truth predicate has an extension [Horsten] |
| 15374 | Truth has no 'nature', but we should try to describe its behaviour in inferences [Horsten] |
| 15348 | Propositions have sentence-like structures, so it matters little which bears the truth [Horsten] |
| 15333 | Modern correspondence is said to be with the facts, not with true propositions [Horsten] |
| 15337 | The correspondence 'theory' is too vague - about both 'correspondence' and 'facts' [Horsten] |
| 15334 | The coherence theory allows multiple coherent wholes, which could contradict one another [Horsten] |
| 15336 | The pragmatic theory of truth is relative; useful for group A can be useless for group B [Horsten] |
| 15354 | Tarski's hierarchy lacks uniform truth, and depends on contingent factors [Horsten] |
| 15340 | Tarski Bi-conditional: if you'll assert φ you'll assert φ-is-true - and also vice versa [Horsten] |
| 15345 | Semantic theories have a regress problem in describing truth in the languages for the models [Horsten] |
| 15373 | Axiomatic approaches avoid limiting definitions to avoid the truth predicate, and limited sizes of models [Horsten] |
| 15346 | Axiomatic approaches to truth avoid the regress problem of semantic theories [Horsten] |
| 15371 | An axiomatic theory needs to be of maximal strength, while being natural and sound [Horsten] |
| 15332 | 'Reflexive' truth theories allow iterations (it is T that it is T that p) [Horsten] |
| 15361 | A good theory of truth must be compositional (as well as deriving biconditionals) [Horsten] |
| 15350 | The Naďve Theory takes the bi-conditionals as axioms, but it is inconsistent, and allows the Liar [Horsten] |
| 15351 | Axiomatic theories take truth as primitive, and propose some laws of truth as axioms [Horsten] |
| 15367 | By adding truth to Peano Arithmetic we increase its power, so truth has mathematical content! [Horsten] |
| 15330 | Friedman-Sheard theory keeps classical logic and aims for maximum strength [Horsten] |
| 15331 | Kripke-Feferman has truth gaps, instead of classical logic, and aims for maximum strength [Horsten] |
| 15325 | Inferential deflationism says truth has no essence because no unrestricted logic governs the concept [Horsten] |
| 15344 | Deflationism skips definitions and models, and offers just accounts of basic laws of truth [Horsten] |
| 15356 | Deflationism concerns the nature and role of truth, but not its laws [Horsten] |
| 15368 | This deflationary account says truth has a role in generality, and in inference [Horsten] |
| 15358 | Deflationism says truth isn't a topic on its own - it just concerns what is true [Horsten] |
| 15359 | Deflation: instead of asserting a sentence, we can treat it as an object with the truth-property [Horsten] |
| 10688 | 'Equivocation' is when terms do not mean the same thing in premises and conclusion [Beall/Restall] |
| 15329 | Nonclassical may accept T/F but deny applicability, or it may deny just T or F as well [Horsten] |
| 10888 | Sets can be defined by 'enumeration', or by 'abstraction' (based on a property) [Zalabardo] |
| 10889 | The 'Cartesian Product' of two sets relates them by pairing every element with every element [Zalabardo] |
| 10890 | A 'partial ordering' is reflexive, antisymmetric and transitive [Zalabardo] |
| 10886 | Determinacy: an object is either in a set, or it isn't [Zalabardo] |
| 10887 | Specification: Determinate totals of objects always make a set [Zalabardo] |
| 10690 | Formal logic is invariant under permutations, or devoid of content, or gives the norms for thought [Beall/Restall] |
| 10897 | A first-order 'sentence' is a formula with no free variables [Zalabardo] |
| 15326 | Doubt is thrown on classical logic by the way it so easily produces the liar paradox [Horsten] |
| 10691 | Logical consequence needs either proofs, or absence of counterexamples [Beall/Restall] |
| 10893 | Γ |= φ for sentences if φ is true when all of Γ is true [Zalabardo] |
| 10899 | Γ |= φ if φ is true when all of Γ is true, for all structures and interpretations [Zalabardo] |
| 10695 | Logical consequence is either necessary truth preservation, or preservation based on interpretation [Beall/Restall] |
| 15341 | Deduction Theorem: ψ only derivable from φ iff φ→ψ are axioms [Horsten] |
| 10689 | A step is a 'material consequence' if we need contents as well as form [Beall/Restall] |
| 10896 | Propositional logic just needs ¬, and one of ∧, ∨ and → [Zalabardo] |
| 15328 | A theory is 'non-conservative' if it facilitates new mathematical proofs [Horsten] |
| 10898 | The semantics shows how truth values depend on instantiations of properties and relations [Zalabardo] |
| 10902 | We can do semantics by looking at given propositions, or by building new ones [Zalabardo] |
| 15349 | It is easier to imagine truth-value gaps (for the Liar, say) than for truth-value gluts (both T and F) [Horsten] |
| 10892 | We make a truth assignment to T and F, which may be true and false, but merely differ from one another [Zalabardo] |
| 10696 | A 'logical truth' (or 'tautology', or 'theorem') follows from empty premises [Beall/Restall] |
| 10895 | 'Logically true' (|= φ) is true for every truth-assignment [Zalabardo] |
| 10900 | Logically true sentences are true in all structures [Zalabardo] |
| 10894 | A sentence-set is 'satisfiable' if at least one truth-assignment makes them all true [Zalabardo] |
| 15366 | Satisfaction is a primitive notion, and very liable to semantical paradoxes [Horsten] |
| 10901 | Some formulas are 'satisfiable' if there is a structure and interpretation that makes them true [Zalabardo] |
| 10693 | Models are mathematical structures which interpret the non-logical primitives [Beall/Restall] |
| 10903 | A structure models a sentence if it is true in the model, and a set of sentences if they are all true in the model [Zalabardo] |
| 15353 | The first incompleteness theorem means that consistency does not entail soundness [Horsten] |
| 15355 | Strengthened Liar: 'this sentence is not true in any context' - in no context can this be evaluated [Horsten] |
| 15364 | English expressions are denumerably infinite, but reals are nondenumerable, so many are unnameable [Horsten] |
| 10692 | Hilbert proofs have simple rules and complex axioms, and natural deduction is the opposite [Beall/Restall] |
| 10891 | If a set is defined by induction, then proof by induction can be applied to it [Zalabardo] |
| 15360 | ZFC showed that the concept of set is mathematical, not logical, because of its existence claims [Horsten] |
| 15369 | Set theory is substantial over first-order arithmetic, because it enables new proofs [Horsten] |
| 15370 | Predicativism says mathematical definitions must not include the thing being defined [Horsten] |
| 15338 | We may believe in atomic facts, but surely not complex disjunctive ones? [Horsten] |
| 15363 | In the supervaluationist account, disjunctions are not determined by their disjuncts [Horsten] |
| 15362 | If 'Italy is large' lacks truth, so must 'Italy is not large'; but classical logic says it's large or it isn't [Horsten] |
| 15372 | Some claim that indicative conditionals are believed by people, even though they are not actually held true [Horsten] |
| 15347 | A theory of syntax can be based on Peano arithmetic, thanks to the translation by Gödel coding [Horsten] |