“Preserve the deposit of faith,” the Church has been told. She cannot look on silently when her doctrines are being falsified and denied, when the most venerable sphere of theology is made the stamping ground for immature minds and a laboratory for all kinds of experiments. When _Zola’s_ novel, “Rome,” had been put on the Index, the atheistic literary critic, _Sarcey_, made the following comment: “If my own criticisms of literature are regarded by many people as highest decisions, why should a positive criticism be looked upon as monstrous just because it comes from the Pope? It is my aim to guard good taste in literature, and it is the aim of the Pope to guard the true faith” (Allgemeine Rundschau, 1908, 828). Every social authority must interfere when its foundations are attacked. A church that tolerates false doctrines cannot be the teacher that Christ sent to the nations. As a matter of fact the Index has from the first helped in no small degree to keep the Catholic doctrine pure, to induce caution in reading certain authors, and to keep awake in the faithful that aversion against immoral and irreligious writings which is the characteristic of Catholics, and which has rescued the faith for thousands. To judge the Index fairly one must be convinced that the preservation of true Christian doctrine is its highest aim. Then the zeal of the Catholic Church will be intelligible. Of course, he who thinks that the true weal of mankind consists in the speedy emancipation from all Christian dogma, he who holds the task of science to be the establishment of a new “scientific view of the world,” he who no longer knows faith, will see in the Index nothing but restraint. But, whoever is of a different view will not take offence at the restriction of the freedom of writing and reading when it is productive of higher good. Freedom of science cannot be unrestricted, especially in regard to teaching; the welfare of humanity must be considered. Moreover, the Index concerns almost exclusively theology and some branches of philosophy, the rest of the profane sciences but little or not at all; the scientific works prohibited, however, are not removed from scientific perusal: only permission is necessary, and this is granted without difficulty and without cost. It is true, an error on the part of the Church authorities is not impossible. We know of such a case, putting on the Index the writings of _Copernicus_, in 1616. But just the circumstance that history knows of but one such case of importance is a clear testimony to the Holy Ghost’s direction of the teaching office even when it is rendering non-infallible decisions. Besides, the damage that might result from a few mistakes would not be so great as the damage resulting if everything were allowed to be written and read.