The main concern of this paper is the design of a noetherian and con uent normalization for LK2 (that is, classical second order predicate logic presented as a sequent calculus). The method we present is powerful: since it allows us to recover as fragments formalisms as seemingly di erent as Girard's LC and Parigot's , FD ([9, 11, 27, 31]), delineates other viable systems as well, and gives mea...