[FOM] 18 Word Proof of the Godel, Rosser and Smullyan Incompleteness Theorems

[Harvey Friedman]

On Jul 17, 2010, at 3:32 PM, steve newberry wrote:

> Kurt Schutte's little Pi-0-2 gem of 1934 is an undecidable sentence,
> in PURE First Order Logic, using a single dyadic predicate, three
> quantifiers, and four literals.

In the sense of undecidable we are talking about in this thread,  
(forall x)(R(x)) is undecidable in pure first order logic. Please  
explain the notion of undecidable you are using.

Harvey Friedman