Many feel that work for Christian unity or ecumenism is not especially urgent or important in the complexities of our contemporary world. So many different issues demand the attention of committed Christians–for example, responding to global crises in which people are suffering, developing strong moral stands on a variety of moral problems and challenges, etc. Such issues must remain of major importance to Christians. However, Christians form the one Body of Christ. If that Body continues to remain divided and fragmented, lacking in unity, concord, and harmony, then Christian witness will be singularly diminished. This book attempts to demonstrate the importance of Christian unity/ecumenism by looking at important contributions of individual theologians and important texts/events, mainly of the twentieth century. The use of this book may help theologians and pastors urge forward the practice of ecumenism so that in God’s time divided Christians may all be one.