This book provides a constructive analysis of Thomas F. Torrance’s ecclesiology. Holding the doctrine of the Trinity to be the ground and grammar of theology, Torrance viewed the doctrine of the Trinity as foundational for all ecclesiological reflection: What does it mean to be the people of the God whom Christians name as Father, Son, and Spirit? Tyler examines Torrance’s development of the rich potential of the metaphor koinonia, involving both a vertical dimension–the Church’s union with Christ through the Spirit–and a horizontal dimension–its visible existence in human history, lived out in space and time, and considers how the relationship between these two dimensions informs the structured forms of the Church’s life, its ecumenical breadth, and its missional vision.