How do you know they are passed on accurately? Glad you asked. First of all, we can read the testimony written by the prophets and apostles in the scriptures:
- John 16:13 When the Spirit of truth comes, he will guide you into all the truth; for he will not speak on his own authority, but whatever he hears he will speak, and he will declare to you the things that are to come.
- John 14:26 But the Counselor, the Holy Spirit, whom the Father will send in my name, he will teach you all things, and bring to your remembrance all that I have said to you.
- Matt 10:20 for it is not you who speak, but the Spirit of your Father speaking through you.
- Isa 35:8 And a highway shall be there, and it shall be called the Holy Way; the unclean shall not pass over it, and fools shall not err therein.
- Matt 28:20 teaching them to observe all things whatsoever I commanded you: and lo, I am with you always, even unto the end of the world.
- 1 Tim 3:15 if I am delayed, you may know how one ought to behave in the household of God, which is the church of the living God, the pillar and bulwark of the truth.
The early Church fathers also affirmed this. For example:
- Ignatius, in around 105 AD, wrote the following: For this end did the Lord allow the ointment to be poured upon His head, John 12:7 that He might breathe immortality into His Church. (Letter to the Ephesians, 17)
- Iraneus, in about 180 AD, wrote the following: But [it has, on the other hand, been shown], that the preaching of the Church is everywhere consistent, and continues in an even course, and receives testimony from the prophets, the apostles, and all the disciples—as I have proved— through [those in] the beginning, the middle, and the end, and through the entire dispensation of God, and that well-grounded system which tends to man's salvation, namely, our faith; which, having been received from the Church, we do preserve, and which always, by the Spirit of God, renewing its youth, as if it were some precious deposit in an excellent vessel, causes the vessel itself containing it to renew its youth also. For this gift of God has been entrusted to the Church, as breath was to the first created man, for this purpose, that all the members receiving it may be vivified; and the [means of] communion with Christ has been distributed throughout it, that is, the Holy Spirit, the earnest of incorruption, the means of confirming our faith, and the ladder of ascent to God. "For in the Church," it is said, "God has set apostles, prophets, teachers," (1 Corinthians 12:28) and all the other means through which the Spirit works; of which all those are not partakers who do not join themselves to the Church, but defraud themselves of life through their perverse opinions and infamous behaviour. For where the Church is, there is the Spirit of God; and where the Spirit of God is, there is the Church, and every kind of grace; but the Spirit is truth. Those, therefore, who do not partake of Him, are neither nourished into life from the mother's breasts, nor do they enjoy that most limpid fountain which issues from the body of Christ; but they dig for themselves broken cisterns out of earthly trenches, and drink putrid water out of the mire, fleeing from the faith of the Church lest they be convicted; and rejecting the Spirit, that they may not be instructed. (Adv. Haer. 3.24.1)
- A couple of decades later, Hippolytus write the following: But we who hope for the Son of God are persecuted and trodden down by those unbelievers. For the wings of the vessels are the churches; and the sea is the world, in which the Church is set, like a ship tossed in the deep, but not destroyed; for she has with her the skilled Pilot, Christ. And she bears in her midst also the trophy (which is erected) over death; for she carries with her the cross of the Lord. For her prow is the east, and her stern is the west, and her hold is the south, and her tillers are the two Testaments; and the ropes that stretch around her are the love of Christ, which binds the Church; and the net which she bears with her is the layer of the regeneration which renews the believing, whence too are these glories. As the wind the Spirit from heaven is present, by whom those who believe are sealed: she has also anchors of iron accompanying her, viz., the holy commandments of Christ Himself, which are strong as iron. She has also mariners on the right and on the left, assessors like the holy angels, by whom the Church is always governed and defended. The ladder in her leading up to the sailyard is an emblem of the passion of Christ, which brings the faithful to the ascent of heaven. And the top-sails aloft upon the yard are the company of prophets, martyrs, and apostles, who have entered into their rest in the kingdom of Christ. (Christ and Antichrist, 59)
There is plenty more, but the bottom line is that Christ promised it. If His Church is in error on a matter of dogma, then Christ lied. If He lied about that, how can we count on anything to be true?