What, then, does the duty to believe require of the faithful Christian? He is required, first of all, to assure himself of the certain credibility of those truths which he is required to believe, and here authentic proofs are offered him. On his perception of the credibility of these truths, he ought to assent to and accept God’s testimony. Hence there should be no coercion to believe without interior conviction, no obstacle put in the way of recognizing the truth. _Where, then, is here any opposition to the lawful freedom of research_, to the right of unimpeded search for the truth? How is reason hindered in its search for the truth when truth is offered it by an infallible authority? We have here no opposition to the laws of reason, but due honour to its sacred rights; no bondage, but elevation and enrichment, completion and crowning of its thought, for the highest truth has been communicated to the reason that it may be of one mind with that Infinite Wisdom which has shaped reason for the truth, and from which it obtains its light as the planet from the sun around which it revolves. Therefore, it cannot be said that “the Catholic resolves to believe as true what the Church teaches in the Apostles’ Creed, but were he offered anything else as Church doctrine he would accept it as well. Hence these doctrines do not express his own personal opinions, they are something extraneous to him.” (_W. Herrmann_, Roemische u. evangelische Sittlichkeit, 3d ed., 1903, p. 3). No, what the Catholic, what any true Christian, believes by faith, that is his innermost conviction, as it is the firm conviction of the historian that what he has drawn from reliable sources is true.—But what if the contrary were offered him? Well, this assumption is absurd; and why? Because God and His Church are infallible, and an infallible authority cannot speak the truth and its contrary at the same time. Much less than a reliable historical witness can testify to the truth and its contrary at the same time. This same conviction gives to the faithful Christian the firm assurance that no certain result of human research will ever come in conflict with his faith, just as the mathematician does not fear that his principle will ever be contradicted by any further work. Truth can never contradict truth. “Thus we believe and thus we teach and herein lies our salvation.” It is the very old conviction of the faithful Christian “that philosophy, that is, the study of wisdom, and religion are not different things.” _Non aliam esse philosophiam, i.e., sapientiae studium et aliam religionem_ (_Augustinus_, De Vera Religione, 5). It is precisely this that enables the believing scientist to devote himself with great freedom and impartiality to research in every field, and to acknowledge any certified result without fear of ever having to stop before a definite conclusion.