A comprehensive and impressive book! All the fundamental results of First-order Logic (Propositional Logic and Predicate Logic), its extension in Peano Arithmetic Axiomatized (PAax) and, finally, a modal analysis of the idea of provability in PAax are subject of a detailed analysis. The whole theoretical developments are both syntactical and semantic, exposed in a variety of theorems, proved in a variety of forms. The Chapter 3, Formal[...]