Abstract: The first part of the book offers a new narrative of the fourth-century Trinitarian controversies. It takes forward modern revisionary scholarship, showing the slow emergence of the theologies that came to constitute pro-Nicene orthodoxy. Ancient heresiological categories, such as ‘Arian’ and ‘Neo-Arian’, are avoided while the unity of ‘Nicene’ theologies is not assumed. The second part offers a new account of the unity in diversity of late fourth-century pro-Nicene theologies. In particular it is argued that the Nicene-Constantinopolitan creed and the statements of unity and plurality in the Trinity, to be found in all pro-Nicene theologians and in Theodosius’ anti-heretical legislation, were intended to be understood in the context of a broad set of theological practices and assumptions. An account of the basic strategies that ground pro-Nicene theology is offered, focusing on common epistemological concerns, a common notion of purification and sanctification, and a common aesthetics of faith. Instructions are provided detailing the Trinitarian theology of Basil of Caesarea, Gregory of Nyssa, and Augustine of Hippo. Throughout the first two parts of the book, a constant concern is to show that the common acceptance of a basic division between Eastern and Western Trinitarian theologies is unsustainable. Finally, the failure of modern Trinitarian theology to engage pro-Nicene theology in a substantial manner is considered.

Keywords: Trinitarian theology, pro-Nicene, Basil of Caesarea, Gregory of Nyssa, Augustine of Hippo, fourth-century, Nicaea