How does the Holy Ghost preserve the Church in the purity of faith?

How does the Holy Ghost preserve the Church in the purity of faith?

By making the head of the Church the infallible teacher in matters of faith and morals. When our Lord Jesus Christ established his Church,  he knew that in all future ages certain men,moved by human weakness or Satanic malice,or by both combined, would arise to corrupt or misinterpret the holy doctrine of his Church; for, men are free agents, and if they will go against God, God, having given them this most glorious privilege of freedom,does not deprive the of it, even when they use it against himself, though, as he has unmistakably warned them, he will call them to strict account for their use or abuse of man’s noblest gift. Now, to remove all doubts about the true meaning of Christ’s doctrine, and to preserve it pure and free even from every chance of error, it was necessary that there should be someone privileged by God to state plainly, with divine certainty, that doctrine in all points of faith and morals; in other words, it was necessary that there should be a supreme judge to decide in all disputed points of divine Law, from whose sentence there should be no appeal. Without this necessary safeguard, the way was forever open to error,and the work of Christ on earth practically useless. If everyman in the country were to explain the laws of the state as he pleases, there would be nothing but confusion and disorder in society. In like manner,if everyman were to interpret the sacred, eternal law of God, the doctrine of Christ, as he pleases, there would be nothing but confusion and disorder in religion. In order to prevent confusion and disorder in society, human wisdom found it necessary to appoint a supreme judge to decide ultimately in all disputed points of civil law. Now, if even human wisdom sees the necessity of appointing a supreme judge, to decide ultimately in all points of civil law,it is most clear that God,who is infinite wisdom,could not and did not fail to appoint a supreme judge to decide ultimately in all points of divine law,in order thus to prevent the possibility of confusion in religion. There never was a time when men were left to themselves to fashion their own religion,to invent their own creed,their own form of worship,and to decide in matters of religion,as they pleased. There always existed on earth a visible teaching authority,to which it was the bounded duty of everyman to submit. During the four thousand years that elapsed before the coming of the Redeemer, the doctrines that were to be believed, the feasts that were to be observed,the sacrifices, the ceremonies of worship,everything connected with religion,were regulated by the living, authoritative voice of the patriarchs, the priests, and the prophets. In the Old Law,God appointed a tribunal,presided over by the high goriest, to judge in all controversies,both of doctrine and morals. The decision of this tribunal was final, and without appeal. The Jewish historian,Josephus, who was well acquainted with the laws and religion of his own nation, says (lib.2,contraAppium): “The high priest offers sacrifice to God before the other priests he guards the laws,judges controversies,punishes the guilty,and whoever disobeys him is punished as one that is impious toward God.” But a still greater authority than Josephus, the word of God itself, bears witness to the fact(Deut.xvii,8-12): “If thou perceive,” says Holy Scripture, “that there be among you a hard and doubtful matter in judgment between blood and blood,cause and cause, and thou seest that the words of the judges within the gates do vary, arise and go up to the place which the Lord thy God shall choose. And thou shalt come to the priests and to the judge,that shall be at that time,and thou shalt ask them,and they shall show thee the truth of the judgment. And thou shalt do whatsoever they say, and thou shalt follow their sentence. Neither shalt thou decline to the right hand,nor to the lefthand. But he that will be proud, and refuse to obey the commandments of the priest who ministers that the time to the Lord thy God,and to the decree of the judge,that man shall die,and thou shalt takeaway the evil from Israel.” Here, then, is clearly a tribunal, appointed by Almighty God himself, to decide in the last resort, a tribunal from whose sentence there is no appeal. Consider carefully every word of the inspired text. There is no exception, the rule is for all; the terrible sentence is pronounced against every transgressor: whosoever shall refuse to abide by the decision of the high-priest, shall die the death. Witness the punishment of Core, Dathan and Abiron: the earth opened and swallowed them up for refusing to obey. This supreme tribunal remained intact until the coming of the Redeemer.

Our Lord himself assures us of this: “The Scribes and Pharisees have sat on the chair of Moses. All things, therefore, whatsoever they shall say to you observe and do.”(Matt,xxiii,2.) Again, our Lord assures us that he came not to destroy the law,but to make it perfect. He therefore established,in the New Law, in his Church, that which, in the Old Law, was most necessary for the preservation of faith and morals, He gave to the whole world an infallible judge and teacher in the person of St. Peter,the head of his Church,and in every successor of St. Peter, to decide ultimately in all points of faith and morals. Christ himself assures us that Peter and his successors are the infallible teachers of his religion. He told St. Peter that,by his prayer to his heavenly Father,he had obtained the gift of infallibility for him and all his successors: “I have prayed for thee(Peter), that thy faith fail not;and thou,being once, converted,confirm thy brethren.”(Luke xxii,31,32.)

(Michael Muller C.SS.R., ” The Church and Her Enemies)