{ localUrl: '../page/59h.html', arbitalUrl: 'https://arbital.com/p/59h', rawJsonUrl: '../raw/59h.json', likeableId: '0', likeableType: 'page', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], pageId: '59h', edit: '2', editSummary: '', prevEdit: '1', currentEdit: '2', wasPublished: 'true', type: 'wiki', title: 'Proof of Gödel's first incompleteness theorem', clickbait: '', textLength: '1482', alias: '59h', externalUrl: '', sortChildrenBy: 'likes', hasVote: 'false', voteType: '', votesAnonymous: 'false', editCreatorId: 'JaimeSevillaMolina', editCreatedAt: '2016-10-11 20:24:50', pageCreatorId: 'JaimeSevillaMolina', pageCreatedAt: '2016-07-10 04:05:09', seeDomainId: '0', editDomainId: 'AlexeiAndreev', submitToDomainId: '0', isAutosave: 'false', isSnapshot: 'false', isLiveEdit: 'true', isMinorEdit: 'false', indirectTeacher: 'false', todoCount: '4', isEditorComment: 'false', isApprovedComment: 'true', isResolved: 'false', snapshotText: '', anchorContext: '', anchorText: '', anchorOffset: '0', mergedInto: '', isDeleted: 'false', viewCount: '32', text: '##Weak form\nThe weak Gödel's first incompleteness theorem states that every [ $\\omega$-consistent] [ axiomatizable] extension of minimal arithmetic is incomplete.\n\nLet $T$ extend [-minimal_arithmetic], and let $Prv_{T}$ be the [5gt standard provability predicate] of $T$. \n\nThen we apply the [59c diagonal lemma] to get $G$ such that $T\\vdash G\\iff \\neg Prv_{T}(G)$.\n\nWe assert that the sentence $G$ is undecidable in $T$. We prove it by contradiction:\n\nSuppose that $T\\vdash G$. Then $Prv_ {T}(G)$ is correct, and as it is a $\\exists$-rudimentary sentence then it is [every_true_e_rudimentary_sentence_is_provable_in_minimal_arithmetic provable in minimal arithmetic], and thus in $T$. So we have that $T\\vdash Prv_ {T}(G)$ and also by the construction of $G$ that $T\\vdash \\neg Prv_{T}(G)$, contradicting that $T$ is consistent.\n\nNow, suppose that $T\\vdash \\neg G$. Then $T\\vdash Prv_{T}(G)$. But then as $T$ is consistent there cannot be a standard proof of $G$, so if $Prv_{T}(x)$ is of the form $\\exists y Proof_{T}(x,y)$ then for no natural number $n$ it can be that $T\\vdash Proof_ {T}(\\ulcorner G\\urcorner,n)$, so $T$ is $\\omega$-inconsistent, in contradiction with the hypothesis.\n\n##Strong form\n\n> Every [5km consistent] and [-axiomatizable] extension of [-minimal_arithmetic] is [complete incomplete].\n\nThis theorem follows as a consequence of the [ undecidability of arithmetic] combined with the lemma stating that [ any complete axiomatizable theory is undecidable]\n', metaText: '', isTextLoaded: 'true', isSubscribedToDiscussion: 'false', isSubscribedToUser: 'false', isSubscribedAsMaintainer: 'false', discussionSubscriberCount: '1', maintainerCount: '1', 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: [ 'godels_first_incompleteness_theorem' ], commentIds: [], questionIds: [], tagIds: [], relatedIds: [], markIds: [], explanations: [], learnMore: [], requirements: [], subjects: [], lenses: [], lensParentId: 'godels_first_incompleteness_theorem', 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: '20114', pageId: '59h', userId: 'JaimeSevillaMolina', edit: '2', type: 'newEdit', createdAt: '2016-10-11 20:24:50', auxPageId: '', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '20113', pageId: '59h', userId: 'JaimeSevillaMolina', edit: '0', type: 'newParent', createdAt: '2016-10-11 20:16:21', auxPageId: 'godels_first_incompleteness_theorem', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '16343', pageId: '59h', userId: 'JaimeSevillaMolina', edit: '1', type: 'newEdit', createdAt: '2016-07-10 04:05:09', auxPageId: '', oldSettingsValue: '', newSettingsValue: '' } ], feedSubmissions: [], searchStrings: {}, hasChildren: 'false', hasParents: 'true', redAliases: {}, improvementTagIds: [], nonMetaTagIds: [], todos: [], slowDownMap: 'null', speedUpMap: 'null', arcPageIds: 'null', contentRequests: {} }