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16 votes
2 answers
2k views

Could Kronecker accept a proof of Goodstein's theorem?

A famous result of Goodstein asserts that the Goodstein sequence of integers terminates. For a precise statement and a short proof, see https://en.wikipedia.org/wiki/Goodstein%27s_theorem. A well ...
Piotr Hajlasz's user avatar
3 votes
0 answers
301 views

What does second order set theory give us that is new?

There is a natural analogy between the theories PA and ZFC. See the linked question by Gro-Tsen here. Peano arithmetic (PA) is a first order approximation to the natural numbers. As is well known, ...
Pace Nielsen's user avatar
  • 18.7k
1 vote
1 answer
396 views

Complete and consistent first-order theories that contain interesting phenomena

Gödel has shown that a consistent recursively axiomatizable first-order theory that can interpret Robinson arithmetic is incomplete. I think there is some sentimental value in working with a theory ...
user avatar
1 vote
0 answers
117 views

Can this type theory interpret second order arithmetic?

Language: multi-sorted first order logic with equality and membership, where for each natural $t$ there is a set $x^t$ of sort $t$. Equality "$=$" only occurs between variables of the same ...
Zuhair Al-Johar's user avatar