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the mathematical discipline that applies mathematical methods to the study of mathematical theories themselves.

3 votes

How can you formalize the metamathematics conventionally used to state Godel’s theorem?

I think this question is clearly asking for provability logic. This is the basic modal logic K with the additional axiom $$\square(\square A \to A) \to \square A.$$ "$\square A$" is interpreted as " …
Nik Weaver's user avatar
  • 42.8k
12 votes

Which kind of foundation are mathematicians using when proving metatheorems?

One direction could go like this. Let ${\rm ZFC}^+$ be the theory in the language of set theory augmented by a constant symbol ${\bf M}$ with the axioms $\bullet$ every axiom of ${\rm ZFC}$ $\bullet …
Nik Weaver's user avatar
  • 42.8k
4 votes

How necessary is Godel's Condensation Lemma

It's been 25 years since I struggled through it, but I clearly remember that Godel's book Consistency of the Axiom of Choice and of the Generalized Continuum Hypothesis with the Axioms of Set Theory g …
Nik Weaver's user avatar
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6 votes

Formal proof of Con(ZFC) => Con(ZFC + not CH) in ZFC

The other answers are perfectly correct, but I'd like to add that the implication Con(ZFC) $\to $Con(ZFC + $\neg$CH) is not only provable in ZFC, it is provable in Peano arithmetic. I consider this a …
Nik Weaver's user avatar
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