[FOM] Church-Kleene or Feferman-Schutte

Aatu Koskensilta Aatu.Koskensilta at uta.fi
Tue May 14 16:33:53 EDT 2013

Quoting Sandro Skansi <skansi.sandro at gmail.com>:

> In terms of ordinals, starting from \omega, which one comes first, the
> Church-Kleene ordinal (\omega_1^CK) or the Feferman-Schutte ordinal
> (\Gamma_0)?

   The Feferman-Schütte ordinal. The Church-Kleene ordinal is the  
least upper bound on ordinals for which there is an effective ordinal  
notation system, e.g. proof-theoretic ordinals of various formal  

Aatu Koskensilta (aatu.koskensilta at uta.fi)

"Wovon man nicht sprechen kann, darüber muss man schweigen"
  - Ludwig Wittgenstein, Tractatus Logico-Philosophicus

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