“Thus, he defines the oneness of God not in terms of the Father, but in terms of the whole Godhead. . . . While the eventual settlements would be due more precisely to the work of the three great Cappadocians, Athanasius’s contribution to the theology of the Trinity can scarcely be overestimated. His elaborations of the full deity of the Son and the Spirit in the one being of God, and of the revelations of the three in their mutual coinherence, were quantum advances in understanding and huge milestones on the path to a more accurate view of the Trinity. In addition, he rooted his Trinitarianism in his doctrines of creation and salvation, and turned discussion away from philosophical speculation and back to biblical and theological basis. These were no mean achievements” (Robert Letham, The Holy Trinity, 145).