85 ideas
10073 | There cannot be a set theory which is complete [Smith,P] |
10616 | Second-order arithmetic can prove new sentences of first-order [Smith,P] |
10076 | The 'range' of a function is the set of elements in the output set created by the function [Smith,P] |
10605 | Two functions are the same if they have the same extension [Smith,P] |
10075 | A 'partial function' maps only some elements to another set [Smith,P] |
10074 | A 'total function' maps every element to one element in another set [Smith,P] |
10612 | An argument is a 'fixed point' for a function if it is mapped back to itself [Smith,P] |
10615 | The Comprehension Schema says there is a property only had by things satisfying a condition [Smith,P] |
10595 | A 'theorem' of a theory is a sentence derived from the axioms using the proof system [Smith,P] |
16357 | Mental files are the counterparts of singular terms [Recanati] |
10602 | A 'natural deduction system' has no axioms but many rules [Smith,P] |
10613 | No nice theory can define truth for its own language [Smith,P] |
10078 | An 'injective' ('one-to-one') function creates a distinct output element from each original [Smith,P] |
10077 | A 'surjective' ('onto') function creates every element of the output set [Smith,P] |
10079 | A 'bijective' function has one-to-one correspondence in both directions [Smith,P] |
10070 | If everything that a theory proves is true, then it is 'sound' [Smith,P] |
10086 | Soundness is true axioms and a truth-preserving proof system [Smith,P] |
10596 | A theory is 'sound' iff every theorem is true (usually from true axioms and truth-preservation) [Smith,P] |
10598 | A theory is 'negation complete' if it proves all sentences or their negation [Smith,P] |
10597 | 'Complete' applies both to whole logics, and to theories within them [Smith,P] |
10069 | A theory is 'negation complete' if one of its sentences or its negation can always be proved [Smith,P] |
10609 | Two routes to Incompleteness: semantics of sound/expressible, or syntax of consistency/proof [Smith,P] |
10080 | 'Effective' means simple, unintuitive, independent, controlled, dumb, and terminating [Smith,P] |
10087 | A theory is 'decidable' if all of its sentences could be mechanically proved [Smith,P] |
10088 | Any consistent, axiomatized, negation-complete formal theory is decidable [Smith,P] |
10081 | A set is 'enumerable' is all of its elements can result from a natural number function [Smith,P] |
10083 | A set is 'effectively enumerable' if a computer could eventually list every member [Smith,P] |
10084 | A finite set of finitely specifiable objects is always effectively enumerable (e.g. primes) [Smith,P] |
10085 | The set of ordered pairs of natural numbers <i,j> is effectively enumerable [Smith,P] |
10601 | The thorems of a nice arithmetic can be enumerated, but not the truths (so they're diffferent) [Smith,P] |
10600 | Being 'expressible' depends on language; being 'capture/represented' depends on axioms and proof system [Smith,P] |
10599 | For primes we write (x not= 1 ∧ ∀u∀v(u x v = x → (u = 1 ∨ v = 1))) [Smith,P] |
10610 | The reals contain the naturals, but the theory of reals doesn't contain the theory of naturals [Smith,P] |
10619 | The truths of arithmetic are just true equations and their universally quantified versions [Smith,P] |
10618 | All numbers are related to zero by the ancestral of the successor relation [Smith,P] |
10608 | The number of Fs is the 'successor' of the Gs if there is a single F that isn't G [Smith,P] |
10849 | Baby arithmetic covers addition and multiplication, but no general facts about numbers [Smith,P] |
10850 | Baby Arithmetic is complete, but not very expressive [Smith,P] |
10852 | Robinson Arithmetic (Q) is not negation complete [Smith,P] |
10851 | Robinson Arithmetic 'Q' has basic axioms, quantifiers and first-order logic [Smith,P] |
10068 | Natural numbers have zero, unique successors, unending, no circling back, and no strays [Smith,P] |
10603 | The logic of arithmetic must quantify over properties of numbers to handle induction [Smith,P] |
10848 | Multiplication only generates incompleteness if combined with addition and successor [Smith,P] |
10604 | Incompleteness results in arithmetic from combining addition and successor with multiplication [Smith,P] |
10617 | The 'ancestral' of a relation is a new relation which creates a long chain of the original relation [Smith,P] |
16360 | Identity statements are informative if they link separate mental files [Recanati] |
16374 | There is a continuum from acquaintance to description in knowledge, depending on the link [Recanati] |
18409 | Indexicals apply to singular thought, and mental files have essentially indexical features [Recanati] |
16354 | Indexicality is closely related to singularity, exploiting our direct relations with things [Recanati] |
16371 | Files can be confused, if two files correctly have a single name, or one file has two names [Recanati] |
16373 | Encylopedic files have further epistemic links, beyond the basic one [Recanati] |
16375 | Singular thoughts need a mental file, and an acquaintance relation from file to object [Recanati] |
16377 | Expected acquaintance can create a thought-vehicle file, but without singular content [Recanati] |
16378 | An 'indexed' file marks a file which simulates the mental file of some other person [Recanati] |
16387 | Reference by mental files is Millian, in emphasising acquaintance, rather than satisfaction [Recanati] |
16358 | The reference of a file is fixed by what it relates to, not the information it contains [Recanati] |
16361 | A mental file treats all of its contents as concerning one object [Recanati] |
16367 | There are transient 'demonstrative' files, habitual 'recognitional' files, cumulative 'encyclopedic' files [Recanati] |
16368 | Files are hierarchical: proto-files, then first-order, then higher-order encyclopedic [Recanati] |
16370 | A file has a 'nucleus' through its relation to the object, and a 'periphery' of links to other files [Recanati] |
16381 | The content of thought is what is required to understand it (which involves hearers) [Recanati] |
16365 | Mental files are individual concepts (thought constituents) [Recanati] |
16356 | There may be two types of reference in language and thought: descriptive and direct [Recanati] |
16393 | In super-direct reference, the referent serves as its own vehicle of reference [Recanati] |
16386 | Direct reference is strong Millian (just a tag) or weak Kaplanian (allowing descriptions as well) [Recanati] |
16372 | Sense determines reference says same sense/same reference; new reference means new sense [Recanati] |
16388 | We need sense as well as reference, but in a non-descriptive form, and mental files do that [Recanati] |
16359 | Sense is a mental file (not its contents); similar files for Cicero and Tully are two senses [Recanati] |
16355 | Problems with descriptivism are reference by perception, by communications and by indexicals [Recanati] |
16348 | Descriptivism says we mentally relate to objects through their properties [Recanati] |
16384 | Definite descriptions reveal either a predicate (attributive use) or the file it belongs in (referential) [Recanati] |
16352 | A rigid definite description can be attributive, not referential: 'the actual F, whoever he is….' [Recanati] |
16353 | Singularity cannot be described, and it needs actual world relations [Recanati] |
16382 | Fregean modes of presentation can be understood as mental files [Recanati] |
16389 | If two people think 'I am tired', they think the same thing, and they think different things [Recanati] |
16363 | Indexicals (like mental files) determine their reference relationally, not by satisfaction [Recanati] |
16364 | Indexical don't refer; only their tokens do [Recanati] |
16351 | In 2-D semantics, reference is determined, then singularity by the truth of a predication [Recanati] |
16350 | Two-D semantics is said to help descriptivism of reference deal with singular objects [Recanati] |
16380 | Russellian propositions are better than Fregean thoughts, by being constant through communication [Recanati] |
6613 | The natural kinds are objects, processes and properties/relations [Ellis] |
6616 | Least action is not a causal law, but a 'global law', describing a global essence [Ellis] |
6615 | A species requires a genus, and its essence includes the essence of the genus [Ellis] |
6614 | A hierarchy of natural kinds is elaborate ontology, but needed to explain natural laws [Ellis] |
6612 | Without general principles, we couldn't predict the behaviour of dispositional properties [Ellis] |