This thesis considers how religious diversification has shaped the roles of clergy and seminaries. The focus of this qualitative, interview-based study is seminaries and clergy affiliated with various denominations of Judaism and Protestant Christianity in greater London and New York City. Religiously diversifying societies in the US and England have brought forth new challenges for clergy and seminaries, prompting new questions about how or why a faith community should or should not engage with diversity in the public square. This study investigates how seminaries and individual members of the clergy, as sources of religious authority, are responding to religious diversification in different ways – the former sluggish to recognise the impact of religious diversification in curriculum and pedagogical structures and the latter seeing it as a resource for social action initiatives, local networks, and political activism. This has created a gap between training and practice whereby clergy have assumed greater religious authority in religious life. Beyond contributing to the field of sociology of religion, this thesis concludes by allowing the experience of clergy in interreligious engagement to inform appropriate pedagogies that could be employed by seminaries.