John Cassian - On the Incarnation of the Lord (Against Nestorius)
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 views of East and West. Unsurprisingly, for one such as Cassian who was so concerned with Christian sanctity, it places special emphasis on the difference between the personal divinity of Christ and the indwelling of the Word in the saints—for the personal divinity of Christ is what indeed makes it possible for Christ to be said to dwell within those saints who tread the heights of union with God. What Cassian lacks in the precision of an Athanasius or a Maximus the Confessor, he makes up for in the verve of his argumentation.