It was this very thought that moved _Leo XIII._ to open the Vatican Archives for freest research to friend and enemy,—the clearest proof that could possibly be given that the Church does not fear historical truth. In his letter of admonition, of August 18, 1883, urging the fostering of historiography, the same Pope gives the following rules for the Catholic scientist: “The first law of history is that it must not say anything false; the second, that it must not be afraid of saying the truth, lest a suspicion of partiality and unfairness arise.” An excellent example of the application of these rules is found in _L. v. Pastor’s_ “History of the Popes,” especially in what he says about _Alexander VI._ and _Leo X._ In his historical investigation of private revelations, such as those of _St. Gertrude_, _St. Mechtild_, _Bl. Juliana of Liège_, or of relics and objects of veneration, the historian is likewise not restricted by Church-direction. Having merely the task of preserving the treasure of the faith received from Christ and the Apostles, the Church in her function as Teacher never vouches for the divine origin of new, private revelations, nor for the accuracy of pious traditions of another kind. True, she decides authoritatively whether private revelations contain anything against faith and morals, but she decides nothing more. If she accepts such revelations or traditions as genuine, she claims for the facts in question only that human faith which corresponds to their historical proof.