Is there not a difference though between what the successors taught and what the original apostles taught? For example, the apostles never taught anything about the assumption of Mary but some “successor” at a later time did. These 2 teachings are not the same thing.
While all New Revelation ended with the death of the last apostle, do you not think it is possible that the Holy Spirit is still leading the Church to all truth? Does not the Holy Spirit teach you new things daily? Weekly? But the Holy Spirit hasn’t lead a whole Church? Those promises only apply to individuals?
So you have issues with the assumption or that Catholics teach that it is true? Since scripture does in fact have assumptions of others in scripture I assume that is is the later?
But the teaching itself was not taught by the original apostles themselves. Correct?
We don’t have any record of it no. If anyone knew though, it would be John and in Revelations, as you know, Catholics claim that some of it applies to Mary.
But again, do you not believe that you are being led by the Holy Spirit to all truth? Do you not “discover” new things daily when you read scripture? And even if the apostles completely understood all of Christ’s teachings, do you really believe all that they taught, fully understood everything? Or is it as scripture says, that they were not ready to hear everything He had to say but He will send the Holy Spirit to lead and guide us?
The catholic church doesn’t get everything wrong.
And we had to get much right or the world would have been bereft of any Christians at all for 1500 years.
Is it not true you have no teachings of the original apostles outside the NT?
No. That is not true. Infant baptism is a direct teaching of the Apostles but is not explicit in scripture, (unless you are a sacramental Protestant, Catholic or Orthodox then it is quite clear

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It was passed down “orally” or more probably, just by actions as we believe that they baptized infants. We also believe the Prayer to the Saints, or asking saints to pray for us was a direct teaching of the apostles, passed down orally, in scripture directly in the deuterocanicals, and implicit in scripture.
What i believe has ultimate authority is what the original apostles taught in the NT.
But who has the ulitimate authority to interpret correctly what those teachings are? Nowhere in scripture, does scripture itself claim that the written word in and of itself has ultimate authority and nor does it claim to be self-interpretative.
Jesus established a Church, a teaching authority to take the disputes that He knew would arise among His followers.
Apostolic Church
Jn 15;16 - Jesus chose special men to be his Apostles
Jn 20:21 - Jesus gave the Apostles his own mission
Lk 22:29-3 - Jesus gave them a kingdom
Mt 16:18 - Jesus built Church on Peter, the rock
Jn 10:16 - one shepherd to shepherd Christ’s sheep
Lk 22:32, Jn 21:17 - Peter appointed to be chief shepherd
Eph 4;11 - church leaders are hierarchical
1Tim 3:1, 8; 5:17 - identifies roles of bishops, priests, deacons
Tit 1:5 - commission for bishops to ordain priests
Authoritative Church
Mt 28:18-20 - Jesus delegates all power to Apostles
Jn 20:23 - power to forgive sin
1Cor 11:23-24 - power to offer sacrifice (Eucharist)
Lk 10:16 - power to speak with Christ’s voice
Mt 18:18 - power to legislate
Mt 18:17 - power to discipline
It is those documents alone that are inspired-inerrant. Now do you think those that came later that have “Apostolic succession” is at the same level as the inspried-inerrant scriptures of the original apostles?
We would agree that it is the NT alone that are inspired and inerrant and do not put them on the same inspired level as that of scripture.
However, we do put them over the writings of other Christians who today teach things that are contrary to things taught by those who were taught by the apostles. Who do you think knew more about infant baptism, someone taught by the apostles who wrote about infant baptisms or someone interpreting scripture from scripture alone? What about the Real Presence of Christ? Do you think that those who write today it is only symbolic are more reliable than those who learned from the apostles? Asking saints to pray for us?
We can show you all of those things from scripture. We can show you ECF writings. Yet you still choose to believe the writings and interpretations of people who came much later.
If you do this for things like infant baptism and the Real presence, how on earth can we get you to understand the teachings of Mary:shrug: