105 ideas
18019 | People have dreams which involve category mistakes [Magidor] |
17998 | Category mistakes are either syntactic, semantic, or pragmatic [Magidor] |
18011 | Category mistakes seem to be universal across languages [Magidor] |
18012 | Category mistakes as syntactic needs a huge number of fine-grained rules [Magidor] |
18013 | Embedded (in 'he said that…') category mistakes show syntax isn't the problem [Magidor] |
18021 | Category mistakes are meaningful, because metaphors are meaningful category mistakes [Magidor] |
18015 | The normal compositional view makes category mistakes meaningful [Magidor] |
18017 | If a category mistake is synonymous across two languages, that implies it is meaningful [Magidor] |
18031 | If a category mistake has unimaginable truth-conditions, then it seems to be meaningless [Magidor] |
18030 | A good explanation of why category mistakes sound wrong is that they are meaningless [Magidor] |
18032 | Category mistakes are neither verifiable nor analytic, so verificationism says they are meaningless [Magidor] |
18034 | Category mistakes play no role in mental life, so conceptual role semantics makes them meaningless [Magidor] |
18037 | Maybe when you say 'two is green', the predicate somehow fails to apply? [Magidor] |
18039 | If category mistakes aren't syntax failure or meaningless, maybe they just lack a truth-value? [Magidor] |
18016 | Two good sentences should combine to make a good sentence, but that might be absurd [Magidor] |
18058 | Maybe the presuppositions of category mistakes are the abilities of things? [Magidor] |
18041 | Category mistakes suffer from pragmatic presupposition failure (which is not mere triviality) [Magidor] |
18056 | Category mistakes because of presuppositions still have a truth value (usually 'false') [Magidor] |
18055 | In 'two is green', 'green' has a presupposition of being coloured [Magidor] |
18057 | 'Numbers are coloured and the number two is green' seems to be acceptable [Magidor] |
18059 | The presuppositions in category mistakes reveal nothing about ontology [Magidor] |
9535 | 'Contradictory' propositions always differ in truth-value [Lemmon] |
9509 | That proposition that both P and Q is their 'conjunction', written P∧Q [Lemmon] |
9511 | We write the conditional 'if P (antecedent) then Q (consequent)' as P→Q [Lemmon] |
9510 | That proposition that either P or Q is their 'disjunction', written P∨Q [Lemmon] |
9512 | We write the 'negation' of P (not-P) as ¬ [Lemmon] |
9513 | We write 'P if and only if Q' as P↔Q; it is also P iff Q, or (P→Q)∧(Q→P) [Lemmon] |
9514 | If A and B are 'interderivable' from one another we may write A -||- B [Lemmon] |
9508 | The sign |- may be read as 'therefore' [Lemmon] |
9516 | A 'well-formed formula' follows the rules for variables, ¬, →, ∧, ∨, and ↔ [Lemmon] |
9517 | The 'scope' of a connective is the connective, the linked formulae, and the brackets [Lemmon] |
9519 | A 'substitution-instance' is a wff formed by consistent replacing variables with wffs [Lemmon] |
9529 | A wff is 'inconsistent' if all assignments to variables result in the value F [Lemmon] |
9531 | 'Contrary' propositions are never both true, so that ¬(A∧B) is a tautology [Lemmon] |
9534 | Two propositions are 'equivalent' if they mirror one another's truth-value [Lemmon] |
9530 | A wff is 'contingent' if produces at least one T and at least one F [Lemmon] |
9532 | 'Subcontrary' propositions are never both false, so that A∨B is a tautology [Lemmon] |
9533 | A 'implies' B if B is true whenever A is true (so that A→B is tautologous) [Lemmon] |
9528 | A wff is a 'tautology' if all assignments to variables result in the value T [Lemmon] |
9518 | A 'theorem' is the conclusion of a provable sequent with zero assumptions [Lemmon] |
9401 | ∨E: Derive C from A∨B, if C can be derived both from A and from B [Lemmon] |
9396 | DN: Given A, we may derive ¬¬A [Lemmon] |
9393 | A: we may assume any proposition at any stage [Lemmon] |
9399 | ∧E: Given A∧B, we may derive either A or B separately [Lemmon] |
9398 | ∧I: Given A and B, we may derive A∧B [Lemmon] |
9397 | CP: Given a proof of B from A as assumption, we may derive A→B [Lemmon] |
9394 | MPP: Given A and A→B, we may derive B [Lemmon] |
9402 | RAA: If assuming A will prove B∧¬B, then derive ¬A [Lemmon] |
9395 | MTT: Given ¬B and A→B, we derive ¬A [Lemmon] |
9400 | ∨I: Given either A or B separately, we may derive A∨B [Lemmon] |
9521 | 'Modus tollendo ponens' (MTP) says ¬P, P ∨ Q |- Q [Lemmon] |
9522 | 'Modus ponendo tollens' (MPT) says P, ¬(P ∧ Q) |- ¬Q [Lemmon] |
9525 | We can change conditionals into negated conjunctions with P→Q -||- ¬(P ∧ ¬Q) [Lemmon] |
9524 | We can change conditionals into disjunctions with P→Q -||- ¬P ∨ Q [Lemmon] |
9523 | De Morgan's Laws make negated conjunctions/disjunctions into non-negated disjunctions/conjunctions [Lemmon] |
9527 | The Distributive Laws can rearrange a pair of conjunctions or disjunctions [Lemmon] |
9526 | We can change conjunctions into negated conditionals with P→Q -||- ¬(P → ¬Q) [Lemmon] |
9537 | Truth-tables are good for showing invalidity [Lemmon] |
9538 | A truth-table test is entirely mechanical, but this won't work for more complex logic [Lemmon] |
9536 | If any of the nine rules of propositional logic are applied to tautologies, the result is a tautology [Lemmon] |
9539 | Propositional logic is complete, since all of its tautologous sequents are derivable [Lemmon] |
13909 | Write '(∀x)(...)' to mean 'take any x: then...', and '(∃x)(...)' to mean 'there is an x such that....' [Lemmon] |
13902 | 'Gm' says m has property G, and 'Pmn' says m has relation P to n [Lemmon] |
13911 | The 'symbols' are bracket, connective, term, variable, predicate letter, reverse-E [Lemmon] |
13910 | Our notation uses 'predicate-letters' (for 'properties'), 'variables', 'proper names', 'connectives' and 'quantifiers' [Lemmon] |
13904 | Universal Elimination (UE) lets us infer that an object has F, from all things having F [Lemmon] |
13906 | With finite named objects, we can generalise with &-Intro, but otherwise we need ∀-Intro [Lemmon] |
13908 | UE all-to-one; UI one-to-all; EI arbitrary-to-one; EE proof-to-one [Lemmon] |
13901 | Predicate logic uses propositional connectives and variables, plus new introduction and elimination rules [Lemmon] |
13903 | Universal elimination if you start with the universal, introduction if you want to end with it [Lemmon] |
13905 | If there is a finite domain and all objects have names, complex conjunctions can replace universal quantifiers [Lemmon] |
13900 | 'Some Frenchmen are generous' is rendered by (∃x)(Fx→Gx), and not with the conditional → [Lemmon] |
18040 | Intensional logic maps logical space, showing which predicates are compatible or incompatible [Magidor] |
9520 | The paradoxes of material implication are P |- Q → P, and ¬P |- P → Q [Lemmon] |
17997 | Some suggest that the Julius Caesar problem involves category mistakes [Magidor] |
18060 | We can explain the statue/clay problem by a category mistake with a false premise [Magidor] |
18020 | Propositional attitudes relate agents to either propositions, or meanings, or sentence/utterances [Magidor] |
18035 | Two sentences with different meanings can, on occasion, have the same content [Magidor] |
18018 | To grasp 'two' and 'green', must you know that two is not green? [Magidor] |
18008 | Generative semantics says structure is determined by semantics as well as syntactic rules [Magidor] |
18010 | 'John is easy to please' and 'John is eager to please' have different deep structure [Magidor] |
18053 | The semantics of a sentence is its potential for changing a context [Magidor] |
18000 | Weaker compositionality says meaningful well-formed sentences get the meaning from the parts [Magidor] |
17999 | Strong compositionality says meaningful expressions syntactically well-formed are meaningful [Magidor] |
18014 | Understanding unlimited numbers of sentences suggests that meaning is compositional [Magidor] |
18001 | Are there partial propositions, lacking truth value in some possible worlds? [Magidor] |
18036 | A sentence can be meaningful, and yet lack a truth value [Magidor] |
18051 | In the pragmatic approach, presuppositions are assumed in a context, for successful assertion [Magidor] |
18043 | The infelicitiousness of trivial truth is explained by uninformativeness, or a static context-set [Magidor] |
18042 | The infelicitiousness of trivial falsity is explained by expectations, or the loss of a context-set [Magidor] |
18047 | A presupposition is what makes an utterance sound wrong if it is not assumed? [Magidor] |
18048 | A test for presupposition would be if it provoked 'hey wait a minute - I have no idea that....' [Magidor] |
18049 | The best tests for presupposition are projecting it to negation, conditional, conjunction, questions [Magidor] |
18050 | If both s and not-s entail a sentence p, then p is a presupposition [Magidor] |
18054 | Why do certain words trigger presuppositions? [Magidor] |
18024 | One theory says metaphors mean the same as the corresponding simile [Magidor] |
18023 | Theories of metaphor divide over whether they must have literal meanings [Magidor] |
18025 | The simile view of metaphors removes their magic, and won't explain why we use them [Magidor] |
18026 | Maybe a metaphor is just a substitute for what is intended literally, like 'icy' for 'unemotional' [Magidor] |
18028 | Gricean theories of metaphor involve conversational implicatures based on literal meanings [Magidor] |
18029 | Non-cognitivist views of metaphor says there are no metaphorical meanings, just effects of the literal [Magidor] |
18022 | Metaphors tend to involve category mistakes, by joining disjoint domains [Magidor] |
18027 | Metaphors as substitutes for the literal misses one predicate varying with context [Magidor] |
1748 | Archelaus was the first person to say that the universe is boundless [Archelaus, by Diog. Laertius] |
5989 | Archelaus said life began in a primeval slime [Archelaus, by Schofield] |