A Catholic apologist fails in his duty to-day if he writes merely to edify the faithful. Granting that the history of the Inquisition will reveal things we never dreamed of, our prejudices must not prevent an honest facing of the facts. We ought to dread nothing more than the reproach that we are afraid of the truth. "We can understand," says Yves Le Querdec,[1] "why our forefathers did not wish to disturb men's minds by placing before them certain questions. I believe they were wrong, for all questions that can be presented will necessarily be presented some day or other. If they are not presented fairly by those who possess the true solution, or who honestly look for it, they will be by their enemies. For this reason we think that not only honesty but good policy require us to tell the world all the facts.... Everything has been said, or will be said some day.... What the friends of the Church will not mention will be spread broadcast by her enemies. And they will make such an outcry over their discovery, that their words will reach the most remote corners and penetrate the deafest ears. We ought not to be afraid to-day of the light of truth; but fear rather the darkness of lies and errors." [1] _Univers_, June 2, 1906. In a word, the best method of apologetics is to tell the whole truth. In our mind, apologetics and history are two sisters, with the same device: "_Ne quid falsi audeat, ne quid veri non audeat historia_."[1] [1] Cicero, De Oratore ii, 15. CONTENTS PREFACE CHAPTER I FIRST PERIOD (I-IV CENTURIES): THE EPOCH OF THE PERSECUTIONS. The Teaching of St. Paul on the Suppression of Heretics The Teaching of Tertullian The Teaching of Origen The Teaching of St. Cyprian The Teaching of Lactantius Constantine, Bishop in Externals The Teaching of St. Hilary CHAPTER II SECOND PERIOD (FROM VALENTINIAN I TO THEODOSIUS II). THE CHURCH AND THE CRIMINAL CODE OF THE CHRISTIAN EMPERORS AGAINST HERESY. Imperial Legislation against Heresy The Attitude of St. Augustine towards the Manicheans St. Augustine and Donatism The Church and the Priscillianists The Early Fathers and the Death Penalty CHAPTER III THIRD PERIOD (A.D. 1100-1250). THE REVIVAL OF THE MANICHEAN HERESIES. Adoptianism and Predestinationism The Manicheans in the West Peter of Bruys Henry of Lausanne Arnold of Brescia Éon de l'Étoile Views of this Epoch upon the Suppression of Heresy CHAPTER IV FOURTH PERIOD (FROM GRATIAN TO INNOCENT III). THE INFLUENCE OF THE CANON LAW, AND THE REVIVAL OF THE ROMAN LAW. Executions of Heretics The Death Penalty for Heretics Legislation of Popes Alexander III and Lucius III and Frederic Barbarossa against Heretics Legislation of Innocent III The First Canonists CHAPTER V THE CATHARAN OR ALBIGENSIAN HERESY: ITS ANTI-CATHOLIC AND ANTI-SOCIAL CHARACTER.