That's presumption. The church received and continuously taught what Jesus taught. There's no need for it all to be written. Again, the church taught it before any of it was written.
It's not presumption.
The Gospel writers recorded Jesus' life, teaching and ministry - as prophesied in the OT. Their purpose in writing was that people should know that Jesus is the Son of God, and Messiah.
Are you saying that there are some things that they thought it important for us to know, but decided not to write them down but rely on Peter, Paul etc to pass them on by word of mouth?
I don't believe that. God doesn't play games - if we needed to know it, Jesus would have taught it and it would be in Scripture.
And so is Tradition considered to be the Word of God.
By you, maybe.
But the bible can't necessarily tell you what it means to say -when controversy comes up as it does in these very forums-over the bible. So the "authority" become whoever thinks that they're interpreting it correctly.
All Christian churches agree with, believe and teach the Gospel - that Jesus was born, was God, lived, taught, healed, died, rose again, ascended, sent his Spirit and will return again one day. THAT is what we have in common. THAT is doctrine. The message of God's love, grace and salvation are recorded in the Bible, and that is our final authority. Hence, Moonies are wrong when they claim that Jesus told "Rev" Moon that he had failed. Other cults are wrong when they claim that Jesus wasn't God or there is no Trinity. If I met someone on the streets today who told me that Jesus was an astronaut, ascended back to heaven in a spaceship, will be returning to earth in that same space ship and their church had believed that for the past 1,000 years; I would ask them where that teaching was in the Bible.
No Christian church believes, or teaches, that - so the fact that their church had done so for years, wouldn't mean anything. Plus, they would not be able to find their teaching in Scripture.
May disagree in how to apply the Bible, so we get arguments over baptism, gender of clergy and almost anything that you can think of.
But those things aren't doctrine.
Yes, the OT could be fully explained only in light of the new revelation brought to us by Christ. Much of the NT was written addressing specific matters often to specific audiences. Again, it was not written as a clear, exhaustive catechism.
You're claiming that the church has authority over, and teaches more than, the word of God. I don't accept that.
You're also claiming that we have to take the church's word for what our Lord taught St Peter , which was vitally important but which Peter decided not to write down. Sorry, but that smacks of having personal, private knowledge that no one else can know.
Gnosticism.