The book is an historical survey of 20th Century Roman Catholic Theological Ethics, which is also known as Moral Theology. The author affirms that it is only through historical investigation that we can really understand how this most conservative and negative field in Catholic theology could become by the end of the 20th century the most innovative one. The century begins with moral manuals being translated into the vernacular. After examining some of these manuals, the author turns to other recent works, and makes a crowning synthesis of innovation all developed before, during and soon after the Second World War. Then the author begins with Humanae Vitae and successive encyclicals and analyzes the recent trends in ethical reflection, where he dwells on the importance of the moral judgment of the informed conscience as an important factor in the ethical life of a Christian. Keenan asserts that theological ethics today is historically rooted, but always engaging the present seeking moral truth for the conscience by looking to speak cross-culturally.