The 10th Assembly of the World Council of Churches in Busan, Republic of Korea, presents a unique opportunity to reflect on an ecumenical theology of mission. This article draws on Roman Catholic perspectives and specifically asks how Catholic social teaching can contribute to this international and inclusive discussion. Connecting some central principles of this teaching to the core theme of the Busan assembly, the author argues that the central aim of Catholic social teaching is to proclaim a God of life and build a civilization of love. As it fosters justice and peace, the church seeks to globalize solidarity and make more visible the invisible heart of God.