It’s a good thing that you accept the importance of Apostolic Authority and Apostolic succession.
The matter to be determined is whether a Great Apostacy occurred or was even possible given the promises of Jesus and the intent of the Father.
A total apostasy, as it is commonly understood, is impossible, and there are three reasons for this:
First, the Old Testament prophecies concerning the New Covenant describe it as perpetual and indefectible. For example, Daniel 7:13-14:
‘I saw in the night visions, and behold, with the clouds of heaven there came one like a son of man [Jesus], and he came to the Ancient of Days and was presented before him. And to him was given dominion and glory and kingdom, that all peoples, nations, and languages should serve him; his dominion is an everlasting dominion, which shall not pass away, and his kingdom one that shall not be destroyed.’ (See also Isaiah 9:6-7 and Daniel 2:44.)
Second, the New Testament also describes the Church as indefectible. Yes, there will be apostasies. That is what St. Paul is referring to in 2 Thessalonians. In fact, there will be a major apostasy before the Second Coming according to 2 Thessalonians 2, but never does it say a total apostasy. According to the New Testament, this is impossible! Matt. 28:19-20 says, “'And Jesus came and said to them, ‘All authority in heaven and on earth has been given to me. Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you; and lo, I am with you always, to the close of the age.’” A similar thought can be found in Luke 1:33, where the Angel Gabriel says of Jesus, “And of his kingdom there will be no end.”
Third, Matthew 28:20 says the Lord will be with us,
pasas tas hemaras, or “all the days”! So there’s no room for total apostasy. Christ will be teaching via his apostles and their successors all days even until the end of time!
In Ephesians, St. Paul explicitly tells us the Church will be with us until the end of time. Ephesians 1:22 describes the Church as “[Christ’s] body, the fullness of him who fills all in all.” This Church is ‘built upon the apostles and prophets, Christ Jesus himself being the chief cornerstone’ (2:20). She is described as being so awesome, St. Paul can say “through the Church the manifold wisdom of God might now be made known to the principalities and powers in heavenly places” (3:10). The Church teaches angels!
As we saw before, this true Church must have apostles, prophets, pastors, evangelists and teachers (cf. 4:11). And why, you ask? ‘For the equipment of the saints. . . for building up the body of Christ. . . so that we may no longer be children, tossed to and fro and carried about with every wind of doctrine. . .’ (4:12,14).
So, God gave us the Church that we may know with certainty the truths of the Faith. That’s not the only reason, but it is a central reason. But maybe the most important passage for us in Ephesians is 3:20-21:
“Now to him who by the power at work within us is able to do far more abundantly than all that we ask or think, to him be glory in the Church and in Christ Jesus to all generations, forever and ever. Amen.”
This Church that St. Paul is describing in Ephesians will be here to all generations (
pasas tas geneas, “all the generations”) forever and ever. This eliminates the possibility of a total apostasy for even one generation!
Hope this helps. :tiphat: