Jonsen's work is essentially an essay in definition, or, more accurately perhaps, an attempt at clarification. The concept of responsibility is a fundamental one in ethics, yet, as the author remarks, ""the language of morality is fickle"" and the concept, despite a vast literature, remains nebulous. In his quest for the reconciliation and synthesis of the components of an adequate definition, Jonsen first surveys relevant documents of specifically Christian coloration. The second part of the book turns to the writings of the moral philosophers, ancient and modern. The third, and most impressive, section examines the use of the term ""responsibility"" in the context of a Christian religious ethic, as illustrated by four modern theologians: Bernhard Haering, Bonhoeffer, Niebuhr, and Robert Johann. Having unraveled the concept itself and its significance for Christian ethics, the author then concludes with a reflection on the trends which adoption of of the concept implies. The consideration that this book, because of the limitations of its subject, will interest only professional theologians, and only a small group of them, should not disguise the fact that Father Jonsen's fine work represents a large step forward in a comparatively new, but important field of endeavor.