The essays in this issue of Harvard Theological Review were originally presented at a celebration in honor of Richard R. Niebuhr on the occasion of his retirement as Hollis Professor of Divinity at Harvard Divinity School. On that day, May 7, 1999, many of Dick's colleagues, friends, and students past and present gathered to pay tribute to him and his forty-three years of service at Harvard. The papers that were delivered and the memories that were shared all told of the profound effect that Dick's teaching, scholarship, and friendship has had on those who have had the pleasure of working and talking with him over the years.