Exactly as the title implies, the authors of this study seek to make explicit the way in which the Old Testament is indispensable to a complete understanding of God's purpose with man and man's response to God, as brought to climax and fulfillment in the New Testament. God's promise to man as set forth by the law and the prophets and the history of Israel's mission, and man's rebellion, is the divine burden of the Old Testament. God's promise of redemption in Jesus Christ is the story of the New Testament. The Christian Church is the new Israel in Christ. First, however, comes the Old, and there can be no proper understanding of the one without the other. Dr. Paul Achtemeier is Professor of New Testament at the Lancaster Theological Seminary, and Dr. Elizabeth Achtemeier is lecturer in Old Testament at the same Seminary. They bring a full knowledge of Biblical scholarship to their task, and together produce a book which both clergy and laity will find most useful in grasping the full sweep of God's one, unfolding, loving, purpose for mankind.