{ localUrl: '../page/consistency.html', arbitalUrl: 'https://arbital.com/p/consistency', rawJsonUrl: '../raw/5km.json', likeableId: '0', likeableType: 'page', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], pageId: 'consistency', edit: '1', editSummary: '', prevEdit: '0', currentEdit: '1', wasPublished: 'true', type: 'wiki', title: 'Consistency', clickbait: '', textLength: '942', alias: 'consistency', externalUrl: '', sortChildrenBy: 'likes', hasVote: 'false', voteType: '', votesAnonymous: 'false', editCreatorId: 'JaimeSevillaMolina', editCreatedAt: '2016-07-24 08:48:18', pageCreatorId: 'JaimeSevillaMolina', pageCreatedAt: '2016-07-24 08:48:18', seeDomainId: '0', editDomainId: 'AlexeiAndreev', submitToDomainId: '0', isAutosave: 'false', isSnapshot: 'false', isLiveEdit: 'true', isMinorEdit: 'false', indirectTeacher: 'false', todoCount: '2', isEditorComment: 'false', isApprovedComment: 'true', isResolved: 'false', snapshotText: '', anchorContext: '', anchorText: '', anchorOffset: '0', mergedInto: '', isDeleted: 'false', viewCount: '30', text: 'A consistent [-theory] is one in which there are well-formed statements that you cannot prove from its axioms; or equivalently, that there is no $X$ such that $T\\vdash X$ and $T\\vdash \\neg X$.\n\nFrom the point of view of [-model_theory], a consistent theory is one whose axioms are [-satisfiable]. Thus, to prove that a set of axioms is consistent you can resort to constructing a model using a formal system whose consistency you trust (normally using [set_theory]) in which all the axioms come true.\n\nArithmetic is [ expressive enough] to talk about consistency within itself. If $\\square_{PA}$ represents the [-5gt] in [3ft] then a sentence of the form $\\neg\\square_{PA}(\\ulcorner 0=1\\urcorner)$ represents the consistency of $PA$, since it comes to say that there exists a disprovable sentence for which there is no proof. [ Gödel's second incompleteness theorem] comes to say that such a sentence is not provable from the axioms of $PA$.', metaText: '', isTextLoaded: 'true', isSubscribedToDiscussion: 'false', isSubscribedToUser: 'false', isSubscribedAsMaintainer: 'false', discussionSubscriberCount: '2', maintainerCount: '2', userSubscriberCount: '0', lastVisit: '', hasDraft: 'false', votes: [], voteSummary: 'null', muVoteSummary: '0', voteScaling: '0', currentUserVote: '-2', voteCount: '0', lockedVoteType: '', maxEditEver: '0', redLinkCount: '0', lockedBy: '', lockedUntil: '', nextPageId: '', prevPageId: '', usedAsMastery: 'false', proposalEditNum: '0', permissions: { edit: { has: 'false', reason: 'You don't have domain permission to edit this page' }, proposeEdit: { has: 'true', reason: '' }, delete: { has: 'false', reason: 'You don't have domain permission to delete this page' }, comment: { has: 'false', reason: 'You can't comment in this domain because you are not a member' }, proposeComment: { has: 'true', reason: '' } }, summaries: {}, creatorIds: [ 'JaimeSevillaMolina' ], childIds: [], parentIds: [ 'math', '2h8' ], commentIds: [], questionIds: [], tagIds: [], relatedIds: [], markIds: [], explanations: [], learnMore: [], requirements: [], subjects: [], lenses: [], lensParentId: '', pathPages: [], learnMoreTaughtMap: {}, learnMoreCoveredMap: {}, learnMoreRequiredMap: {}, editHistory: {}, domainSubmissions: {}, answers: [], answerCount: '0', commentCount: '0', newCommentCount: '0', linkedMarkCount: '0', changeLogs: [ { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '17558', pageId: 'consistency', userId: 'EricRogstad', edit: '0', type: 'newParent', createdAt: '2016-07-26 22:39:45', auxPageId: 'math', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '17446', pageId: 'consistency', userId: 'JaimeSevillaMolina', edit: '0', type: 'newParent', createdAt: '2016-07-24 08:48:20', auxPageId: '2h8', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '17444', pageId: 'consistency', userId: 'JaimeSevillaMolina', edit: '1', type: 'newEdit', createdAt: '2016-07-24 08:48:18', auxPageId: '', oldSettingsValue: '', newSettingsValue: '' } ], feedSubmissions: [], searchStrings: {}, hasChildren: 'false', hasParents: 'true', redAliases: {}, improvementTagIds: [], nonMetaTagIds: [], todos: [], slowDownMap: 'null', speedUpMap: 'null', arcPageIds: 'null', contentRequests: {} }