78 ideas
5300 | Philosophers have interpreted the world, but the point is to change it [Marx] |
5297 | Whether human thinking can be 'true' must be decided in practice, not theory [Marx] |
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] |
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] |
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] |
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] |
10079 | A 'bijective' function has one-to-one correspondence in both directions [Smith,P] |
10077 | A 'surjective' ('onto') function creates every element of the output set [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] |
6007 | If you know your father, but don't recognise your father veiled, you know and don't know the same person [Eubulides, by Dancy,R] |
6006 | If you say truly that you are lying, you are lying [Eubulides, by Dancy,R] |
6008 | Removing one grain doesn't destroy a heap, so a heap can't be destroyed [Eubulides, by Dancy,R] |
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] |
10851 | Robinson Arithmetic 'Q' has basic axioms, quantifiers and first-order logic [Smith,P] |
10852 | Robinson Arithmetic (Q) is not negation complete [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] |
22598 | The authentic self exists at the level of class, rather than the individual [Marx, by Dunt] |
5298 | The human essence is not found in individuals but in social relations [Marx] |
23874 | Armies and businesses create moralities in which their activity can do no wrong [Marx, by Weil] |
22001 | The real will of the cooperative will replace the 'will of the people' [Marx] |
21991 | The middle class gain freedom through property, but workers can only free all of humanity [Marx, by Singer] |
21990 | Theory is as much a part of a revolution as material force is [Marx] |
22971 | In moving from capitalism to communism a revolutionary dictatorship of the proletariat is needed [Marx] |
18662 | Liberal freedom is the right to be separate, and ignores the union of man with man [Marx] |
23372 | Liberals want the right to be separate, rather than for people to be united [Marx] |
20576 | Early Marx anticipates communitarian objections to liberalism [Marx, by Oksala] |
21989 | Man is dominated by money, which is the essence of his alienation [Marx] |
22000 | From each according to his ability, to each according to his need [Marx] |
23862 | By saying the material dialectic of history aspires to the best, Marx agreed with capitalism [Weil on Marx] |
21999 | False consciousness results from concealment by the superstructure [Marx, by Singer] |
23875 | Marx says force is everything, and that the weak will become strong, while remaining the weak [Weil on Marx] |
21995 | Must production determine superstructure, or could it be the other way round? [Singer on Marx] |
18653 | Marx rejected equal rights because they never actually treat people as equals [Marx, by Kymlicka] |
20577 | Even decently paid workers still have their produce bought with money stolen from them [Marx] |
22969 | People who only have their labour power are the slaves of those permitting them to work [Marx] |
21996 | Freedom only comes when labour is no longer necessary [Marx] |
22970 | Freedom is making the state subordinate to its society [Marx] |
21994 | The handmill gives feudalism, the steam mill capitalism [Marx] |
20958 | Capitalism changes the world, by socialising the idea of a commodity [Marx, by Bowie] |
23876 | The essence of capitalism is the subordination of people to things [Marx, by Weil] |
20960 | Marx thought capitalism was partly liberating, and could make labour and ownership more humane [Marx, by Bowie] |
22972 | Bourgeois 'freedom of conscience' just tolerates all sorts of religious intolerance [Marx] |
20519 | Marxists say liberal rights are confrontational, and liberal equality is a sham [Marx, by Wolff,J] |
7128 | Religion is the opium of the people, and real happiness requires its abolition [Marx] |
5299 | Religious feeling is social in origin [Marx] |