18 ideas
13838 | A decent modern definition should always imply a semantics [Hacking] |
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] |
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] |
12219 | Whether a modal claim is true depends on how the object is described [Quine, by Fine,K] |
13837 | With a pure notion of truth and consequence, the meanings of connectives are fixed syntactically [Hacking] |
13839 | Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers [Hacking] |
10922 | Objects are the values of variables, so a referentially opaque context cannot be quantified into [Quine] |
13843 | If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking] |
10923 | Aristotelian essentialism says a thing has some necessary and some non-necessary properties [Quine] |
10921 | Necessity can attach to statement-names, to statements, and to open sentences [Quine] |
10924 | Necessity is in the way in which we say things, and not things themselves [Quine] |
13304 | Learned men gain more in one day than others do in a lifetime [Posidonius] |
20820 | Time is an interval of motion, or the measure of speed [Posidonius, by Stobaeus] |