32 ideas
13838 | A decent modern definition should always imply a semantics [Hacking] |
19215 | Arguers often turn the opponent's modus ponens into their own modus tollens [Merricks] |
19205 | 'Snow is white' only contingently expresses the proposition that snow is white [Merricks] |
13833 | 'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking] |
13834 | Gentzen's Cut Rule (or transitivity of deduction) is 'If A |- B and B |- C, then A |- C' [Hacking] |
13835 | Only Cut reduces complexity, so logic is constructive without it, and it can be dispensed with [Hacking] |
19209 | Simple Quantified Modal Logc doesn't work, because the Converse Barcan is a theorem [Merricks] |
19208 | The Converse Barcan implies 'everything exists necessarily' is a consequence of 'necessarily, everything exists' [Merricks] |
11211 | If a sound conclusion comes from two errors that cancel out, the path of the argument must matter [Rumfitt] |
13845 | The various logics are abstractions made from terms like 'if...then' in English [Hacking] |
13840 | First-order logic is the strongest complete compact theory with Löwenheim-Skolem [Hacking] |
13844 | A limitation of first-order logic is that it cannot handle branching quantifiers [Hacking] |
13842 | Second-order completeness seems to need intensional entities and possible worlds [Hacking] |
11210 | Standardly 'and' and 'but' are held to have the same sense by having the same truth table [Rumfitt] |
13837 | With a pure notion of truth and consequence, the meanings of connectives are fixed syntactically [Hacking] |
11212 | The sense of a connective comes from primitively obvious rules of inference [Rumfitt] |
13839 | Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers [Hacking] |
19207 | Sentence logic maps truth values; predicate logic maps objects and sets [Merricks] |
13843 | If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking] |
19214 | In twinning, one person has the same origin as another person [Merricks] |
19217 | I don't accept that if a proposition is directly about an entity, it has a relation to the entity [Merricks] |
19203 | A sentence's truth conditions depend on context [Merricks] |
19200 | Propositions are standardly treated as possible worlds, or as structured [Merricks] |
19206 | 'Cicero is an orator' represents the same situation as 'Tully is an orator', so they are one proposition [Merricks] |
19202 | Propositions are necessary existents which essentially (but inexplicably) represent things [Merricks] |
19204 | True propositions existed prior to their being thought, and might never be thought [Merricks] |
19210 | The standard view of propositions says they never change their truth-value [Merricks] |
19201 | Propositions can be 'about' an entity, but that doesn't make the entity a constituent of it [Merricks] |
19211 | Early Russell says a proposition is identical with its truthmaking state of affairs [Merricks] |
19212 | Unity of the proposition questions: what unites them? can the same constituents make different ones? [Merricks] |
19213 | We want to explain not just what unites the constituents, but what unites them into a proposition [Merricks] |
11214 | We learn 'not' along with affirmation, by learning to either affirm or deny a sentence [Rumfitt] |