Ecce Homo: On the Divine Unity of Christ by Aaron Riches (review)

Modern Christology tends to suffer from a persistent and malignant inclination towards problematic dualisms ultimately aligned with Nestorianism. Such is the diagnosis underlying Aaron Riches's Ecce Homo: On the Divine Unity of Christ, and Riches prescribes as remedy a Christology of divine unity rooted in the insights of Cyril of Alexandria and further articulated by the councils of Chalcedon and Constantinople II and III. Riches's well-researched study is at once systematic, historical, and genealogical, though not always in equal measure. The book includes an Introduction, ten main chapters organized within three parts ("The Unity of Christ," "The Synergy of Christ," and "The Existence of Christ"), an eleventh chapter as a Coda ("The Communion of Jesus and Mary"), and a short Conclusion. Riches moves through thematic divisions mostly chronologically, investigating and reprising the fundamental tensions of Christological debates through the centuries.

The Introduction specifies the unity of Christ as the book's point of departure and notes that "to begin from the unio of humanity with the divine Son is to begin with a paradox" (5). Awareness of this paradox pervades the study and, for Riches, guards against the "false dualisms" inherent in Nestorianism and modernity, dualisms ultimately rooted in monism. The book's primary aim is combating these false dualisms through articulations of this paradoxical unity.

Part I ("The Unity of Christ") includes three chapters that leverage recent work in historical theology to distill basic systematic Christological principles. Chapter 1 ("Against Separation") details the Christological controversy ignited by Nestorius's rejection of the Marian title Theotokos. The chapter offers careful interpretations of Cyril of Alexandria's responses to and efforts against Nestorius, highlighting Cyril's insistence on the oneness of Christ as proclaimed at Nicaea. At issue in the debate between Cyril and Nestorius was the unity and singularity of subject in Christ. Nestorius, and before him Theodore of Mopsuestia, feared that ardent emphasis on this unity and singularity risks the distinction between divinity and humanity in a theologically untenable manner, while Cyril countered that failure to emphasize this unity and singularity undermines the truth of the incarnation and the offer of salvation it inaugurated.

Chapter 2 ("The Humanity of Christ") introduces the crucial concept of communicatio idiomatum, according to which "because of the union of divinity and humanity in Jesus, properties that are properly divine may be predicated of the man Jesus while properties that are properly human may be predicated of the divine person of the Son" (42). After clarifying that and how this does not entail a confusion of divinity and humanity, Riches guides a historical tour through the "concentric circles" of Nestorianism and Pelagianism in order to identify the shared underlying anthropological assumptions as well as how and why those assumptions appeal to modern advocates of a Christology "from below."

Chapter 3 ("Chalcedonian Orthodoxy") frames the famous Chalcedonian "Definition of the Faith" with initial consideration of Eutyches and his misunderstanding of Cyril's formula mia physis. Eutyches's attempted adherence to Cyril led him to profess a tertium quid rather than the hypostatic union by falsely correlating concrete union in hypostasis with the abstract identity of the natures united, an error that combated any problematic separation of the natures with an equally problematic and corrupting identity. Both errors represent inadequate responses to the crucifixion, responses addressed by Chalcedon's Definitio. Riches draws careful and critical attention to some modern tendencies in discussing Chalcedon. One tendency is to focus narrowly on the précis of the Definitio, a focus that excludes the traditional character and aims of the Definitio under the misguided assumption that it strives for a novel formula. Against this, Riches stresses Chalcedon's fundamental dedication to and continuation of Nicea and, even more fundamentally, to apostolic teachings. Another tendency is to frame the Chalcedonian Definitio as a "clash between two internally coherent and disciplined Christological 'schools...