Informal proof of diagonal lemma











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I am reading this proof of the diagonal lemma
and I do not understand what is happening here. Could you informally explain what is the strategy here? I would appreciate it if you went step by step. I am aware of this informal exposition, but I don't think it explains the proof itself.






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    Could you expand on which part of the proof you don't understand? That would help others explain it. There's not really much of an informal strategy, except "construct the thing the theorem says must exist". The construction is hard to discover - it's the kind of proof that you simply check step by step.
    – Carl Mummert
    2 days ago










  • See also the post proving-and-understanding-the-fixed-point-lemma-diagonal-lemma-in-logic
    – Mauro ALLEGRANZA
    yesterday

















up vote
0
down vote

favorite
1












I am reading this proof of the diagonal lemma
and I do not understand what is happening here. Could you informally explain what is the strategy here? I would appreciate it if you went step by step. I am aware of this informal exposition, but I don't think it explains the proof itself.






logic







share|cite|improve this question







New contributor




M. Moe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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  • 1




    Could you expand on which part of the proof you don't understand? That would help others explain it. There's not really much of an informal strategy, except "construct the thing the theorem says must exist". The construction is hard to discover - it's the kind of proof that you simply check step by step.
    – Carl Mummert
    2 days ago










  • See also the post proving-and-understanding-the-fixed-point-lemma-diagonal-lemma-in-logic
    – Mauro ALLEGRANZA
    yesterday















up vote
0
down vote

favorite
1









up vote
0
down vote

favorite
1






1





I am reading this proof of the diagonal lemma
and I do not understand what is happening here. Could you informally explain what is the strategy here? I would appreciate it if you went step by step. I am aware of this informal exposition, but I don't think it explains the proof itself.






logic







share|cite|improve this question







New contributor




M. Moe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











I am reading this proof of the diagonal lemma
and I do not understand what is happening here. Could you informally explain what is the strategy here? I would appreciate it if you went step by step. I am aware of this informal exposition, but I don't think it explains the proof itself.






logic




logic






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M. Moe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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M. Moe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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Check out our Code of Conduct.








  • 1




    Could you expand on which part of the proof you don't understand? That would help others explain it. There's not really much of an informal strategy, except "construct the thing the theorem says must exist". The construction is hard to discover - it's the kind of proof that you simply check step by step.
    – Carl Mummert
    2 days ago










  • See also the post proving-and-understanding-the-fixed-point-lemma-diagonal-lemma-in-logic
    – Mauro ALLEGRANZA
    yesterday
















  • 1




    Could you expand on which part of the proof you don't understand? That would help others explain it. There's not really much of an informal strategy, except "construct the thing the theorem says must exist". The construction is hard to discover - it's the kind of proof that you simply check step by step.
    – Carl Mummert
    2 days ago










  • See also the post proving-and-understanding-the-fixed-point-lemma-diagonal-lemma-in-logic
    – Mauro ALLEGRANZA
    yesterday










1




1




Could you expand on which part of the proof you don't understand? That would help others explain it. There's not really much of an informal strategy, except "construct the thing the theorem says must exist". The construction is hard to discover - it's the kind of proof that you simply check step by step.
– Carl Mummert
2 days ago




Could you expand on which part of the proof you don't understand? That would help others explain it. There's not really much of an informal strategy, except "construct the thing the theorem says must exist". The construction is hard to discover - it's the kind of proof that you simply check step by step.
– Carl Mummert
2 days ago












See also the post proving-and-understanding-the-fixed-point-lemma-diagonal-lemma-in-logic
– Mauro ALLEGRANZA
yesterday






See also the post proving-and-understanding-the-fixed-point-lemma-diagonal-lemma-in-logic
– Mauro ALLEGRANZA
yesterday












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You could try §47 of the notes Gödel Without Tears, which is still rather terse buy the notation might be a bit more helpful.



https://www.logicmatters.net/resources/pdfs/gwt/GWT2f.pdf






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    You could try §47 of the notes Gödel Without Tears, which is still rather terse buy the notation might be a bit more helpful.



    https://www.logicmatters.net/resources/pdfs/gwt/GWT2f.pdf






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      up vote
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      You could try §47 of the notes Gödel Without Tears, which is still rather terse buy the notation might be a bit more helpful.



      https://www.logicmatters.net/resources/pdfs/gwt/GWT2f.pdf






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        up vote
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        You could try §47 of the notes Gödel Without Tears, which is still rather terse buy the notation might be a bit more helpful.



        https://www.logicmatters.net/resources/pdfs/gwt/GWT2f.pdf






        share|cite|improve this answer














        You could try §47 of the notes Gödel Without Tears, which is still rather terse buy the notation might be a bit more helpful.



        https://www.logicmatters.net/resources/pdfs/gwt/GWT2f.pdf







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