Here’s an example of what Doug Hofstadter writes in I Am A Strange Loop. Kurt Goedel discovered that Principia Mathematica by Bertrand Russell does provide reference to itself. So Russell in his book yields the propositions and their proofs, and then Goedel assigns specific numbers to proofs and therefore proves that there is a proof that they are in fact, provable
Here’s an example of what Doug Hofstadter writes in I Am A Strange Loop. Kurt Goedel discovered that Principia Mathematica by Bertrand Russell does provide reference to itself. So Russell in his book yields the propositions and their proofs, and then Goedel assigns specific numbers to proofs and therefore proves that there is a proof that they are in fact, provable