[FOM] strong arithmetical theorems?

[Panu Raatikainen]

Are there natural theorems of ordinary *arithmetic* which are not  
provable in weak theories such as S^1_2, EFA and such (that is,  
theories that can be interpreted in the Robinson Arithmetic Q) but  
require at least RCA_0, or something ?

Best

Panu


-- 
Panu Raatikainen

Ph.D., Docent in Theoretical Philosophy

Department of Philosophy, History, Culture and Art Studies
P.O. Box 24  (Unioninkatu 38 A)
FIN-00014 University of Helsinki
Finland

E-mail: panu.raatikainen at helsinki.fi
http://www.mv.helsinki.fi/home/praatika/