In this study, we have considered if, how, or to what extent emerging Christian expressions within the context of the Emerging Church (EC) movement, and related Emerging Missional partners and postcedents, might reform, contextualize, innovate, or revise Christian forms, language, practices, or doctrines to reform the church and inculturate the gospel in postmodern contexts, while retaining continuity and congruence with apostolicity and orthodoxy. We also wished to see if, how, or to what extent EC voices considered accountability to apostolicity and orthodoxy and, if not, to what they were accountable and also to what extent they remain authentically Christian. We have done so by examining the perspectives of leading EC authors, practitioners, and current and historical conversation partners including Vincent of Lérins and Dietrich Bonhoeffer, using historical, theological, ethnographic and narrative inquiry and analysis methods. Our review of literature from EC authors provides insights into debates that led to fracturing of the EC movement and that offer challenges to orthodoxy. Our analysis also reveals methods EC authors appealed to in order to justify their views, or defense or revisions of core historic doctrines. When they rarely appealed to orthodoxy, there were two common but divergent approaches in which orthodoxy was either viewed as a system of beliefs, in which one could treat orthodox doctrines trans-subjectively, or else as being subjectively grounded in the incarnate Christ, in which accountability to Christ was primarily evidenced in materialist acts. We also placed our analysis of key EC sources and their approaches to apostolicity and orthodoxy in conversation with the historical perspectives of Vincent of Lérins and Dietrich Bonhoeffer, as well as with current EC practitioners, via an ethnographic questionnaire. We found that Vincent’s method of consensual orthodoxy, instead of seeing orthodoxy as a system of universal beliefs, or as entirely subjective, appeared to center orthodoxy in the unified life of the Body of Christ in which doctrine may grow and, yet, its apostolic meaning is safeguarded by requiring Christians to surrender current interpretations of Scripture to the universal ecumenical consensus of the Body of Christ through history. Then too, our review of Bonhoeffer’s works reveals the ways that he provides room for questioning and flexibility, while holding that the creedal beliefs and sacred practices of the apostolic faith must be surrendered to as-is, as agents of revelation. In further analysis of primary sources and ethnographic responses, the study also reveals a third EC approach to apostolicity and orthodoxy, in which, in synergy with Vincent and Bonhoeffer, orthodox doctrine is seen as the unified faith, obedience, worship, and witness of the Body of Christ, and in which body doctrine may contextually grow in faithful alignment with apostolicity. Additionally, we considered Vincent’s method as providing orthodox EC voices a rule to guide contextual listening, inculturation and growth of doctrine while ensuring continuity and congruity with apostolicity. / Thesis (PhD)--University of Pretoria, 2018. / Church History and Church Policy / PhD / Unrestricted