Full Idea
Any consistent, axiomatized, negation-complete formal theory is decidable.
Gist of Idea
Any consistent, axiomatized, negation-complete formal theory is decidable
Source
Peter Smith (Intro to Gödel's Theorems [2007], 03.6)
Book Reference
Smith,Peter: 'An Introduction to Gödel's Theorems' [CUP 2007], p.26