This is a far more specific book than its title indicates. It is, according to the author, ""the first complete book in English to deal with the problem of establishing norms for the interpretation of Papal encyclicals."" A technical, juridicial work, it is concerned with very recent practical questions. In fact Mr. Wills begins his study by discussing the dispute which arose between William F. Buckley and the Catholic press over the National Review's flippant attitude toward Mater et Magistra,-- (""Mater, sl, Magistra, no""). He defends Buckley's right to disagree with certain aspects of Pope John's encyclical (though he regrets the irreverence of that perennial enfant terrible). This brings him to a critical examination of the positions of those liberal Catholics who have, for some time, been taking what Mr. Wills considers interpretative liberties with the social encyclicals. Having pointed out the errors of interpreting Papal teaching in terms of one's own political viewpoint, Mr. Wills performs the truly genuine service of explaining Papal terminology, the binding force of the encyclicals, the general relation of Papal teaching to political disagreements and basic conflicting views of the Church's relation to the world. The author recognizes that there will always be differences in the application of principles and he is very logical and incisive in pointing out where others go astray. As explication this is useful. He reveals, however, the quality of his own judgment (to single out one recent controversial instance) in defending the default of Pius XII with regard to the Nazi policy toward the Jews.