"If the adversary," he says, "do but grant any portion of the divine revelation, we have an argument against him. Against a heretic we can employ Scripture authority, and against those who deny one article we can use another. If our opponent rejects divine revelation altogether, then there is no way left to prove the Articles of Faith by reasoning. We can only solve the difficulties which are raised against the faith." Care must be taken, then, that beginners approach the study of the Bible well prepared and furnished; otherwise, just hopes will be frustrated, or perchance--and this is worse--they will unthinkingly risk the danger of error, and fall an easy prey to the sophisms and labored erudition of the rationalists. The best preparation will be a conscientious application to philosophy and theology under the guidance of St. Thomas of Aquin, and a thorough training therein--as We Ourselves have elsewhere shown and prescribed. By this means, both in biblical studies and in that part of Theology which is called _Positive_, they will pursue the right path and make solid progress. To prove, to expound, to illustrate Catholic doctrine by the legitimate and skilful interpretation of the Bible is much; but there is a second part of the subject of equal importance and of equal laboriousness,--the maintenance in the strongest possible way of the fulness of its authority. This cannot be done completely or satisfactorily except by means of the living teaching authority of the Church herself. The Church, by reason of her wonderful propagation, her shining sanctity, and her inexhaustible fecundity in good, her Catholic unity, and her unshaken stability, is herself a great and perpetual motive of credibility, and an unassailable testimony of her own divine mission. But since the divine and infallible teaching authority of the Church rests also on the authority of Holy Scripture, the first thing to be done is to vindicate the trustworthiness of the sacred records at least as human documents. From this can clearly be proved, as from primitive and authentic testimony, the divinity and the mission of Christ our Lord, the institution of a hierarchical Church, and the primacy of Peter and his successors. It is most desirable, therefore, that there should be many members of the clergy well prepared to enter upon a contest of this nature, and to repulse the attacks of the enemy, chiefly trusting in that armor of God which is recommended by the Apostle, but at the same time not unacquainted with the more modern methods of attack. This is beautifully alluded to by St. John Chrysostom. Describing the duties of priests, he says: "We must use our every endeavor that the 'word of God may dwell in us abundantly.' Not merely for one kind of light must we be prepared, for the contest is many-sided, and the enemy is of every sort. They do not all use the same weapons, nor do all make their onset in the same way.