13.1 Syntax of Proofs
13.1 Syntax of Proofs A proof system needs a precise notion of proof. Informally, a proof is an argument that shows why a conclusion follows. Formally, a proof is a finite object built according to fixed rules. The syntax of proofs describes the shape of these objects. Formulas and Judgments A proof does not manipulate meanings directly. It manipulates formulas. A typical formula is written: $$ A $$ A derivability...