This dissertation examines the connection between church-world theology and the practice of Christian peacemaking. The new theology of church and world developed in Gaudium et Spes laid the foundation for a practice of peacemaking as an active form of engagement in the world. Yet the theological tensions present in that document have continued to play out in debates over theology and practice today, as seen in the divergent viewpoints of George Weigel, Bryan Hehir, and Michael Baxter. Yves Congar offers a richer church-world theology that more fruitfully integrates the tensions in church-world theology and lays a foundation for a practice of peacemaking that is both authentically Christian and practically effective. The lay Catholic Community of Sant’Egidio, upon which Congar was a profound influence, embodies a model of peacemaking that reflects this church-world theology and offers some important signposts for an ethic of Christian peacemaking.