In a word, the Sovereign Pontiff is to the Church, though in a more eminent degree, what the Supreme Court is to the United States. We have an instrument called the Constitution of the United States, which is the charter of our civil rights and liberties. If a controversy arise regarding a constitutional clause, the question is referred in the last resort, to the Supreme Court at Washington. The Chief Justice, with his associate judges, examines into the case and then pronounces judgment upon it; and this decision is final, irrevocable and practically infallible. If there were no such court to settle constitutional questions, the Constitution itself would soon become a dead letter. Every litigant would conscientiously decide the dispute in his own favor and anarchy, separation and civil war would soon follow. But by means of this Supreme Court disputes are ended, and the political union of the States is perpetuated. There would have been no civil war in 1861 had our domestic quarrel been submitted to the legitimate action of our highest court of judicature, instead of being left to the arbitrament of the sword. The revealed Word of God is the constitution of the Church. This is the _Magna Charta_ of our Christian liberties. The Pope is the official guardian of our religious constitution, as the Chief Justice is the guardian of our civil constitution. When a dispute arises in the Church regarding the sense of Scripture the subject is referred to the Pope for final adjudication. The Sovereign Pontiff, before deciding the case, gathers around him his venerable colleagues, the Cardinals of the Church; or he calls a council of his associate judges of faith, the Bishops of Christendom; or he has recourse to other lights which the Holy Ghost may suggest to him. Then, after mature and prayerful deliberation, he pronounces judgment and his sentence is final, irrevocable and infallible. If the Catholic Church were not fortified by this Divinely-established supreme tribunal, she would be broken up, like the sects around her, into a thousand fragments and religious anarchy would soon follow. But by means of this infallible court her marvellous unity is preserved throughout the world. This doctrine is the keystone in the arch of Catholic faith, and, far from arousing opposition, it ought to command the unqualified admiration of every reflecting mind. These explanations being premised, let us now briefly consider the grounds of the doctrine itself.