Before revision: Completeness (logic) Syntax (logic) Consistency Decidability (logic) Deductive system Interpretation (logic) Cantor's theorem Church's theorem Church's thesis Effective method Formal system Gödel's completeness theorem Gödel's first incompleteness theorem Gödel's second incompleteness theorem Independence (mathematical logic) Logical consequence Löwenheim–Skolem theorem Metalanguage Metasyntactic variable Metatheorem Object language Symbol (formal) Type–token distinction Use–mention distinction Well-formed formula Proof theory Proof theory – The study of deductive apparatus.
After revision: – see metalanguageCompleteness (logic) Syntax (logic) Consistency Decidability (logic) Deductive system Interpretation (logic) Cantor's theorem Church's theorem Church's thesis Effective method Formal system Gödel's completeness theorem Gödel's first incompleteness theorem Gödel's second incompleteness theorem Independence (mathematical logic) Logical consequence Löwenheim–Skolem theorem Metalanguage Metasyntactic variable Metatheorem Object language Symbol (formal) Type–token distinction Use–mention distinction Well-formed formula Proof theory Proof theory – The study of deductive apparatus.