Full Idea
Baby Arithmetic is negation complete, so it can prove every claim (or its negation) that it can express, but it is expressively extremely impoverished.
Gist of Idea
Baby Arithmetic is complete, but not very expressive
Source
Peter Smith (Intro to Gödel's Theorems [2007], 08.3)
Book Reference
Smith,Peter: 'An Introduction to Gödel's Theorems' [CUP 2007], p.55