Example image of eyePlorer eyePlorer map for 'First-order logic': Computer science Linguistics Mathematics Philosophy Predicate logic Domain of discourse Propositional calculus Deductive system Validity Automated theorem proving Decidability (logic) Compactness theorem Löwenheim–Skolem theorem Metalogic Proof theory Axiomatic system Foundations of mathematics Peano axioms Zermelo–Fraenkel set theory Morley's categoricity theorem Natural number Real line Second-order logic Predicate (mathematical logic) Quantification Material conditional Universal quantification Existential quantification Semantics Syntax Formal language Exclusive or Sheffer stroke Non-logical symbol Signature (logic) Arity Binary relation Group (mathematics) Ordered field Empty set Uncountable set Propositional variable Arithmetic Power set Set theory Formation rule Formal grammar Context-free grammar Recursive definition Term (mathematics)