Lob's Theorem


Lob's Theorem asserts that no formal system T can prove statements of the form "If A is provable in T, then A is true" unless it is also capable of proving A directly. It can be seen as a generalization of Godel's Second Incompleteness Theorem.


This concept has the prerequisites:


  • Know the statement of Lob's Theorem and why it is significant
  • Show how to derive Godel's Second Incompleteness Theorem as a special case of Lob's Theorem
  • Prove Lob's Theorem

Core resources (read/watch one of the following)


Notes on Logic (2013)
Lecture notes for a course on first order logic.
Author: Henry Cohn


See also

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