FOL Fitting

Isabelle FOL Fitting: First-Order Logic According to Fitting. We present a formalization of parts of Melvin Fitting’s book ”First-Order Logic and Automated Theorem Proving”. The formalization covers the syntax of first-order logic, its semantics, the model existence theorem, a natural deduction proof calculus together with a proof of correctness and completeness, as well as the Löwenheim-Skolem theorem.