Doctrine is central to Christian discipleship and maturity. Unfortunately, it is often sidelined in churches' teaching ministry as irrelevant or impractical. Countering this, leading church historian Douglas Sweeney defines doctrine as church teaching intended for the shaping of daily faith and practice. The Substance of Our Faith addresses introductory issues in the study and application of historical doctrine, incorporating a unique global and catholic perspective. It addresses the Spirit's role in the rise of doctrine in the early church, the authority of Scripture and tradition in the development of doctrine, the challenges of doing global historical theology, the nature and purpose of doctrine, and implications for teaching the faith today. Specifically, Sweeney advocates that those who teach the Christian faith in all churches do so in communion with the saints who have come before. A future volume by the author will narrate the actual history of doctrinal teaching around the world.