21 ideas
13838 | A decent modern definition should always imply a semantics [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] |
13833 | 'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking] |
8859 | The main modal logics disagree over three key formulae [Yablo] |
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] |
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] |
13843 | If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking] |
8865 | If 'the number of Democrats is on the rise', does that mean that 50 million is on the rise? [Yablo] |
8863 | We must treat numbers as existing in order to express ourselves about the arrangement of planets [Yablo] |
8862 | Platonic objects are really created as existential metaphors [Yablo] |
8864 | We quantify over events, worlds, etc. in order to make logical possibilities clearer [Yablo] |
8858 | Philosophers keep finding unexpected objects, like models, worlds, functions, numbers, events, sets, properties [Yablo] |
22371 | Determinism threatens free will if actions can be causally traced to external factors [Foot] |
8861 | Hardly a word in the language is devoid of metaphorical potential [Yablo] |
22372 | Not all actions need motives, but it is irrational to perform troublesome actions with no motive [Foot] |
22373 | People can act out of vanity without being vain, or even vain about this kind of thing [Foot] |