As the world becomes more complex because of scientific advances, the need for up to date application of the principles of ethics to the natural order and those of moral theology to the supernatural becomes absolute. Theologians who traditionally move slowly are being required to speed the process. As the study of good and evil, moral theology is the of Christian moral activity. And it must be applicable to the times. The Cardinal compiler of this huge Dictionary has performed a major service by providing the modern day Catholic with discussions of aspects of practical theology which will help to suggest modes of action today in relationships to Society and the Church. Probable are suggested from the principles. There will be room for argument, to be sure. But, at least, the effort has been made. The Dictionary touches on many new developments atom bombing, constitutional immorality, melancholy, to mention but a few which are adequately discussed. An extensive bibliography gives this page volume further strength as a reference. This is a book which should be in any library worthy of such identification. Only the price might keep it from circulation into private homes. A ""magnum opus"", this Dictionary may well become a basic work in this critical area of human activity.