98 ideas
| 13395 | If an analysis shows the features of a concept, it doesn't seem to 'reduce' the concept [Jubien] |
| 7791 | The simplest of the logics based on possible worlds is Lewis's S5 [Lewis,CI, by Girle] |
| 10482 | The logic of ZF is classical first-order predicate logic with identity [Boolos] |
| 9967 | 'Impure' sets have a concrete member, while 'pure' (abstract) sets do not [Jubien] |
| 10492 | A few axioms of set theory 'force themselves on us', but most of them don't [Boolos] |
| 18192 | Do the Replacement Axioms exceed the iterative conception of sets? [Boolos, by Maddy] |
| 7785 | The use of plurals doesn't commit us to sets; there do not exist individuals and collections [Boolos] |
| 10485 | Naïve sets are inconsistent: there is no set for things that do not belong to themselves [Boolos] |
| 10484 | The iterative conception says sets are formed at stages; some are 'earlier', and must be formed first [Boolos] |
| 13547 | Limitation of Size is weak (Fs only collect is something the same size does) or strong (fewer Fs than objects) [Boolos, by Potter] |
| 10699 | Does a bowl of Cheerios contain all its sets and subsets? [Boolos] |
| 9358 | There are several logics, none of which will ever derive falsehoods from truth [Lewis,CI] |
| 13378 | It is a mistake to think that the logic developed for mathematics can clarify language and philosophy [Jubien] |
| 14249 | Boolos reinterprets second-order logic as plural logic [Boolos, by Oliver/Smiley] |
| 10830 | Second-order logic metatheory is set-theoretic, and second-order validity has set-theoretic problems [Boolos] |
| 10225 | Monadic second-order logic might be understood in terms of plural quantifiers [Boolos, by Shapiro] |
| 10736 | Boolos showed how plural quantifiers can interpret monadic second-order logic [Boolos, by Linnebo] |
| 10780 | Any sentence of monadic second-order logic can be translated into plural first-order logic [Boolos, by Linnebo] |
| 10829 | A sentence can't be a truth of logic if it asserts the existence of certain sets [Boolos] |
| 9357 | Excluded middle is just our preference for a simplified dichotomy in experience [Lewis,CI] |
| 10697 | Identity is clearly a logical concept, and greatly enhances predicate calculus [Boolos] |
| 9364 | Names represent a uniformity in experience, or they name nothing [Lewis,CI] |
| 13402 | We only grasp a name if we know whether to apply it when the bearer changes [Jubien] |
| 13405 | The baptiser picks the bearer of a name, but social use decides the category [Jubien] |
| 13399 | Examples show that ordinary proper names are not rigid designators [Jubien] |
| 13398 | We could make a contingent description into a rigid and necessary one by adding 'actual' to it [Jubien] |
| 10832 | '∀x x=x' only means 'everything is identical to itself' if the range of 'everything' is fixed [Boolos] |
| 11115 | 'All horses' either picks out the horses, or the things which are horses [Jubien] |
| 13392 | Philosophers reduce complex English kind-quantifiers to the simplistic first-order quantifier [Jubien] |
| 13671 | Second-order quantifiers are just like plural quantifiers in ordinary language, with no extra ontology [Boolos, by Shapiro] |
| 10267 | We should understand second-order existential quantifiers as plural quantifiers [Boolos, by Shapiro] |
| 10698 | Plural forms have no more ontological commitment than to first-order objects [Boolos] |
| 7806 | Boolos invented plural quantification [Boolos, by Benardete,JA] |
| 9968 | A model is 'fundamental' if it contains only concrete entities [Jubien] |
| 10834 | Weak completeness: if it is valid, it is provable. Strong: it is provable from a set of sentences [Boolos] |
| 13841 | Why should compactness be definitive of logic? [Boolos, by Hacking] |
| 9965 | There couldn't just be one number, such as 17 [Jubien] |
| 10491 | Infinite natural numbers is as obvious as infinite sentences in English [Boolos] |
| 10483 | Mathematics and science do not require very high orders of infinity [Boolos] |
| 10833 | Many concepts can only be expressed by second-order logic [Boolos] |
| 9966 | The subject-matter of (pure) mathematics is abstract structure [Jubien] |
| 10490 | Mathematics isn't surprising, given that we experience many objects as abstract [Boolos] |
| 9962 | How can pure abstract entities give models to serve as interpretations? [Jubien] |
| 9963 | If we all intuited mathematical objects, platonism would be agreed [Jubien] |
| 9964 | Since mathematical objects are essentially relational, they can't be picked out on their own [Jubien] |
| 13404 | To exist necessarily is to have an essence whose own essence must be instantiated [Jubien] |
| 13386 | If objects are just conventional, there is no ontological distinction between stuff and things [Jubien] |
| 10700 | First- and second-order quantifiers are two ways of referring to the same things [Boolos] |
| 13403 | The category of Venus is not 'object', or even 'planet', but a particular class of good-sized object [Jubien] |
| 10488 | It is lunacy to think we only see ink-marks, and not word-types [Boolos] |
| 11116 | Being a physical object is our most fundamental category [Jubien] |
| 10487 | I am a fan of abstract objects, and confident of their existence [Boolos] |
| 9969 | The empty set is the purest abstract object [Jubien] |
| 10489 | We deal with abstract objects all the time: software, poems, mistakes, triangles.. [Boolos] |
| 13375 | The idea that every entity must have identity conditions is an unfortunate misunderstanding [Jubien] |
| 11117 | Haecceities implausibly have no qualities [Jubien] |
| 13393 | Any entity has the unique property of being that specific entity [Jubien] |
| 13388 | It is incoherent to think that a given entity depends on its kind for its existence [Jubien] |
| 13384 | Objects need conventions for their matter, their temporal possibility, and their spatial possibility [Jubien] |
| 13385 | Basically, the world doesn't have ready-made 'objects'; we carve objects any way we like [Jubien] |
| 13383 | If the statue is loved and the clay hated, that is about the object first qua statue, then qua clay [Jubien] |
| 13400 | If one entity is an object, a statue, and some clay, these come apart in at least three ways [Jubien] |
| 13401 | The idea of coincident objects is a last resort, as it is opposed to commonsense naturalism [Jubien] |
| 13380 | Parts seem to matter when it is just an object, but not matter when it is a kind of object [Jubien] |
| 13376 | We should not regard essentialism as just nontrivial de re necessity [Jubien] |
| 13381 | Thinking of them as 'ships' the repaired ship is the original, but as 'objects' the reassembly is the original [Jubien] |
| 13382 | Rearranging the planks as a ship is confusing; we'd say it was the same 'object' with a different arrangement [Jubien] |
| 13379 | If two objects are indiscernible across spacetime, how could we decide whether or not they are the same? [Jubien] |
| 11002 | Equating necessity with informal provability is the S4 conception of necessity [Lewis,CI, by Read] |
| 13394 | Entailment does not result from mutual necessity; mutual necessity ensures entailment [Jubien] |
| 9362 | Necessary truths are those we will maintain no matter what [Lewis,CI] |
| 11119 | De re necessity is just de dicto necessity about object-essences [Jubien] |
| 7803 | Modal logic began with translation difficulties for 'If...then' [Lewis,CI, by Girle] |
| 13391 | Modality concerns relations among platonic properties [Jubien] |
| 13374 | To analyse modality, we must give accounts of objects, properties and relations [Jubien] |
| 11118 | Modal propositions transcend the concrete, but not the actual [Jubien] |
| 11108 | Your properties, not some other world, decide your possibilities [Jubien] |
| 11111 | Modal truths are facts about parts of this world, not about remote maximal entities [Jubien] |
| 11105 | We have no idea how many 'possible worlds' there might be [Jubien] |
| 11109 | If other worlds exist, then they are scattered parts of the actual world [Jubien] |
| 11106 | If all possible worlds just happened to include stars, their existence would be necessary [Jubien] |
| 11107 | If there are no other possible worlds, do we then exist necessarily? [Jubien] |
| 11112 | Possible worlds just give parallel contingencies, with no explanation at all of necessity [Jubien] |
| 11113 | Worlds don't explain necessity; we use necessity to decide on possible worlds [Jubien] |
| 13389 | The love of possible worlds is part of the dream that technical logic solves philosophical problems [Jubien] |
| 13390 | Possible worlds don't explain necessity, because they are a bunch of parallel contingencies [Jubien] |
| 11110 | We mustn't confuse a similar person with the same person [Jubien] |
| 9365 | We can maintain a priori principles come what may, but we can also change them [Lewis,CI] |
| 21500 | We rely on memory for empirical beliefs because they mutually support one another [Lewis,CI] |
| 21501 | If we doubt memories we cannot assess our doubt, or what is being doubted [Lewis,CI] |
| 6556 | If anything is to be probable, then something must be certain [Lewis,CI] |
| 21498 | Congruents assertions increase the probability of each individual assertion in the set [Lewis,CI] |
| 13396 | Analysing mental concepts points to 'inclusionism' - that mental phenomena are part of the physical [Jubien] |
| 5828 | Extension is the class of things, intension is the correct definition of the thing, and intension determines extension [Lewis,CI] |
| 9361 | We have to separate the mathematical from physical phenomena by abstraction [Lewis,CI] |
| 8693 | An 'abstraction principle' says two things are identical if they are 'equivalent' in some respect [Boolos] |
| 13377 | First-order logic tilts in favour of the direct reference theory, in its use of constants for objects [Jubien] |
| 9363 | Science seeks classification which will discover laws, essences, and predictions [Lewis,CI] |