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Gödelian Logic

Edited by Yoav Ravid last updated 21st Dec 2021

Gödelian Logic refers to logic, math, and arguments in the style of Kurt Gödel. Specifically - his two incompleteness theorems, and one completeness theorem. Due to their tricky and subtle nature, his incompleteness theorems are possibly the most misunderstood theorems of all time.

“All the limitative theorems of metamathematics and the theory of computation suggest that once the ability to represent your own structure has reached a certain critical point, that is the kiss of death: it guarantees that you can never represent yourself totally. Gödel’s Incompleteness Theorem, Church’s Undecidability Theorem, Turing’s Halting Theorem, Tarski’s Truth Theorem — all have the flavour of some ancient fairy tale which warns you that “To seek self-knowledge is to embark on a journey which … will always be incomplete, cannot be charted on any map, will never halt, cannot be described.” - Douglas Hofstadter, Gödel, Escher, Bach

Gödel's Completeness Theorem

This theorem is less well known than the other two, which came after it, but also less misunderstood. 

Gödel's First Incompleteness Theorem

Gödel's Second Incompleteness Theorem

 

Probabilistic Solutions

One way you might think to get around Gödel's Incompleteness, is to leave behind logical certainty, and instead assign probabilities to logical statements. 

External Resources:

  • Quanta Magazine: How Gödel's Proof Works
  • Stanford Encyclopedia of Philosophy:
    • Gödel’s Incompleteness Theorems
    • Kurt Gödel (including his completeness theorem)
  • Wikipedia:
    • Incompleteness Theorems
    • Completeness Theorem
    • First-order logic and Second-order logic
    • Kurt Gödel
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Posts tagged Gödelian Logic
112Reflection in Probabilistic Logic
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101[Book review] Gödel, Escher, Bach: an in-depth explainer
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80Godel's Completeness and Incompleteness Theorems
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79Completeness, incompleteness, and what it all means: first versus second order logic
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76A Proof of Löb's Theorem using Computability Theory
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49You Provably Can't Trust Yourself
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45Gödel's Legacy: A game without end
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27MIRI course list book reviews, part 1: Gödel, Escher, Bach
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23What's going on with "provability"?
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17Formalising cousin_it's bounded versions of Gödel's theorem
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16Explained: Gödel's theorem and the Banach-Tarski Paradox
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