The shortest, most direct, most conclusive, and most intelligible method of proving the truth of any system is to find its principle, its fundamental idea, and to establish the reality and certainty of this idea. When this is done, the whole system which is logically and justly built on this foundation is already proved. In the case of the Christian religion, we have only one thing to establish, in order to convince all pagans, Mohammedans, modern Jews, and unbelievers, who are truly rational, of its divine truth. That one thing is the divine mission of Jesus Christ. When that is established, there is but one question which can be reasonably asked--What is the authentic doctrine and law promulgated by Jesus Christ? {196} In the same manner, in order to convince all rational men that the Catholic religion is entirely true, and the real Christianity established by the Apostles, it is only necessary to prove its fundamental principle, the Supremacy of St. Peter and his successors, the Roman Pontiffs. This doctrine, held and understood in its strict and complete Catholic sense, distinguishes the Catholic religion from every other. This once established in the conviction and belief of the mind, the truth of the whole Catholic religion, in all its parts, follows as a necessary consequence. It follows that the communion of which the Pope is the Supreme Head, is the true Church established by Jesus Christ--One, Holy, Catholic, and Apostolic, incapable of falling away, and infallible in doctrine. The foundation of this great and world-wide Church is the Papal Supremacy of St. Peter and his successors, and its principal portion is the Roman See. If I prove that this foundation was laid by Jesus Christ, it will be evident that the Church founded upon it is the true Catholic Church, and the faith of that Church the true Christian and Catholic faith. I will then endeavor to prove, first, that Jesus Christ appointed St. Peter as Prince of the Apostles, His Vicar, and the Supreme Pastor and Ruler of the Church; and, second, that the Bishop of Rome is St. Peter's successor. {197} First, Jesus Christ appointed St. Peter as Prince of the Apostles, His Vicar, and the Supreme Pastor and Ruler of the Church. This will be the theme of the present discourse.