Near the end of his writing career, Cassian the monk was commissioned by the future Pope Leo the Great to reply to the Christological positions of Nestorius. Nestorius saw in Christ two subjects, that of the Word and that of the man Jesus. Cassian's foray into ecclesiastical controversy yields a cannonade of arguments from the Scriptures and the early Fathers, bombarding the Nestorian position with an impassioned rendition of the general Christological...