The importance of Gregory's contribution to the development of the doctrine of deification can hardly be overstated. Gregory was the first theologian to coin the term 'theosis', a term which would become the standard cipher for the doctrine in the later Byzantine tradition. He is one of the most prolific users of deification language in the first four centuries of Christian literature, and his account of deification served as the principal source of the doctrine for its most important Byzantine expositors. Theosis in the Theology of Gregory of Nazianzus elucidates Gregory's contribution to the doctrine's development by providing a comprehensive study of his understanding of salvation as theosis, analysing his thought across his entire corpus and in its historical and intellectual context. In this book, Brendan A. Harris shows that Gregory's theology of deification is centred on the notion of deifying union, a union Gregory understands in terms of Neo-Platonic mixture theory. This notion of the deifying union forms a rich seam that permeates Gregory's soteriological thinking and integrates a diverse range of soteriological motifs into a single, coherent soteriological vision, centred on the creature's reception of and union with divine light. Within this vision, the motif of angelification^—^the transformation of the human being into an angelic or angelomorphic being^—^emerges as an essential, yet largely neglected, aspect of Gregory's concept of deification. For Gregory, deification entails angelification: to be deified is to become like the angels, who are united to God from the moment of their creation, and to share in the angelic vision and worship of God.
