72 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] |
| 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] |
| 10608 | The number of Fs is the 'successor' of the Gs if there is a single F that isn't G [Smith,P] |
| 10618 | All numbers are related to zero by the ancestral of the successor relation [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] |
| 18430 | We accept properties because of type/tokens, reference, and quantification [Edwards] |
| 18432 | Quineans say that predication is primitive and inexplicable [Edwards] |
| 18437 | Resemblance nominalism requires a second entity to explain 'the rose is crimson' [Edwards] |
| 18434 | That a whole is prior to its parts ('priority monism') is a view gaining in support [Edwards] |
| 20547 | We should respect the right of people to live in their own way, even if it is irrational [Swift] |
| 20564 | Anti-colonial movements usually invoke the right of their 'people' to self-determination [Swift] |
| 20535 | Isn't it more rational to maximise the average position, but with a safety net? [Swift] |
| 20537 | Hypothetical contracts have no binding force [Swift] |
| 20542 | Cosmopolitans reject the right of different states to distribute resources in different ways [Swift] |
| 20559 | Democracy is bad, but the other systems are worse [Swift] |
| 20561 | Since all opinions are treated as equal in democracy, it implies there are no right answers [Swift] |
| 20562 | Design your democracy to treat citizens equally, or to produce better citizens? [Swift] |
| 20563 | Design your democracy to yield political stability, or good decisions? [Swift] |
| 20560 | Teledemocracy omits debate and deliberation, which are important parts of good decisions [Swift] |
| 20554 | Multiculturalism is a barrier to the whole state being a community [Swift] |
| 20553 | Liberals mistakenly think individuals choose their values, without reference to the community [Swift] |
| 20556 | The best way to build a cohesive community is to be involved in a war [Swift] |
| 20557 | Membership and inclusion in a community implies non-membership and exclusion [Swift] |
| 20555 | Liberals are concerned to protect individuals from too much community [Swift] |
| 20540 | Redistributing wealth treats some people as means, rather than as ends [Swift] |
| 20551 | Men have had the power to structure all of our social institutions [Swift] |
| 20545 | Maybe a freedom is from a restraint, and also in order to do something [Swift] |
| 20550 | Opportunity should ignore extraneous factors, or foster competence, or ignore all disadvantages [Swift] |
| 20536 | Inequalities are needed, as incentives to do the most important jobs [Swift] |
| 20548 | A person can desire redistibution of wealth, without it being for reasons of equality [Swift] |
| 20541 | You can't necessarily sell your legitimate right to something, even if you produced it [Swift] |
| 20546 | Libertarians about property ignore the fact that private property is a denial of freedoms [Swift] |
| 20533 | Justice can be seen as fairness or entitlement or desert [Swift] |