Full Idea
Since predicate logic merely extends propositional logic, all the axioms of propositional logic are axioms of predicate logic.
Gist of Idea
Predicate logic retains the axioms of propositional logic
Source
Keith Devlin (Goodbye Descartes [1997], Ch. 4)
Book Reference
Devlin,Keith: 'Goodbye Descartes: the end of logic' [Wiley 1997], p.83
A Reaction
See Idea 7798 for the axioms.
Related Idea
Idea 7798 There are three axiom schemas for propositional logic [Girle]