the following must be included. First is his insistence that the natures of Christ must be numbered,92 because the number, when applied properly to Christ’s natures, does not divide.93 Second is his extensive use of the tripartite formula, to which references have already been made. Third is the way in which he uses the notion of perichōrēsis. Perichōrēsis in his Christology is not unilateral—that is, from the divinity to the humanity—but is characterized by mutuality and reciprocity.94 Fourth, and