. "classical natural deduction" . "deductive" . . . . "deduction" . . "Natural deduction" . "natural deduction" . . "traditional deductive" . . "Deduction" . . "Natural deduction#Proofs_and_type_theory" . "Natural deduction" . "natural deductive" . "Natural deduction#Introduction and elimination" . "judgments" . . . . "rule of assumption" . . . "assumption" . "introduction and elimination rules" . "judgment" . "normal forms" . "introduction rules and elimination rules" . . "introduction rule" .