This study of John Calvin's ecclesiology argues that Calvin's idea of the twofold identity of the Church--its spiritual identity as the body of Christ and its functional identity as the mother of all believers--is closely related to his understanding of Christian identity and life, which are initiated and maintained by the grace of the triune God. The anthropological basis of Calvin's idea of the Church has not been examined fully, even though Calvin presents the important concepts of his ecclesiology in light of his anthropological ideas. This study offers an overall evaluation for Calvin's ecclesiology, arguing that it is ultimately his pastoral concern for the Christian and the Church under affliction that both governs his theological understanding of the Church and shapes his proposals for establishing and sustaining the life of the Church in the world.