This begs the question of what does "fully Catholic" mean for believers living in the first four centuries after Christ? ALL the quotes I provided argue for the authority of the Scriptures - and it matters not when they may or may not have been "formally" defined as canonical. These theologians understood and accepted that the word of God WAS sufficient to fully equip the man of God in doctrine, reproof and instructions for righteousness so that one is thoroughly furnished unto all good works.
Justin Could not have been arguing for the formal sufficiency because he died around 164-165 IIRC. The New Testament had not been formally ordered yet. Do you believe that he was saying the OT was sufficient?
Justin, just as did the first century church, received the books of the Old Testament ALONG WITH the writings of the Apostles and disciples who were moved to write by the power and inspiration of the Holy Spirit. That the different churches scattered around the known world had hand copied writings of these and that the theologians and leaders within these churches acknowledged and received the writings as from God - fully authoritative - proves that a later "formally ordered" canon changed NOTHING of what had been accepted until that time. Peter, writing around 67-68 A.D., was able to describe Paul's epistles as "Scripture" and equal to the other divinely-inspired writings is additional proof of this fact.
But you are changing the topic. I pointed out that it was the Catholic Church which defined: The Trinity, the hypostatic union, etc... There were no protestants there to define them.
I wasn't changing the topic but answering your assorted questions, one of which concerned your contention that: "History teaches us that while the writings for the Bible existed at the end of the first century there were also numerous heretical writings that were being accepted. It was up to the successors of the apostles to examine and discern which ones were apostolic in nature and exclude those that were not." The Christians that received the divinely-inspired writings from the Apostles recognized their authority and power because they had the same Holy Spirit within them who illuminated those truths to their hearts. Do you think they couldn't tell the difference between an epistle from the Apostle Peter and the book claiming to be the "Gospel According to Peter"?
Literally everything that you hold as good and true that actually is good and true was defined by the Catholic Church. It is only on the man made novelties that you disagree with the Catholic Church on.
Everything that is good and true regarding our Christian faith - whether or not today's Roman Catholic Church officially believes it - is so because the Word of God either explicitly or implicitly states it. You keep referring to the "Catholic Church" back then and attributing everything about the faith to them, yet it was not the same church as modern-day Catholics think they are part of nor was its success and faithfulness to the truth based upon its submission to the bishop of Rome. What these assemblies of believers agreed upon was what God revealed to them through the teachings and writings of the Apostles and Jesus' direct disciples. That was how there could BE a universal faith that tied ALL followers of Jesus Christ to each other in mutual recognition of the fellowship of the faith. Paul reproved those people who "chose sides", remember? (see I Cor. 3:4-6) They did not invent doctrines, but rather:
For we did not follow cleverly devised tales when we made known to you the power and coming of our Lord Jesus Christ, but we were eyewitnesses of His majesty. (II Peter 1:16)
And
This testimony is true. For this reason reprove them severely so that they may be sound in the faith, not paying attention to Jewish myths and commandments of men who turn away from the truth. (Titus 1:13,14)
And
As I urged you upon my departure for Macedonia, remain on at Ephesus so that you may instruct certain men not to teach strange doctrines, nor to pay attention to myths and endless genealogies, which give rise to mere speculation rather than furthering the administration of God which is by faith. But the goal of our instruction is love from a pure heart and a good conscience and a sincere faith. (I Timothy 1:3-5)
Some yes, but most NO! That is why they had the councils of Hippo and Carthage in 393 and 397 respectively. To settle exactly which books were and were not.
Flash forward a thousand years and you will see that Martin Luther wanted to remove James and Revelation. Do you think they he couldn't tell the difference between an epistle from the Apostle Peter James and the book claiming to be the "Gospel According to Peter? fill in the blank and the real apocalyptic literature.
Why are modern protestants able to discern that they are both scripture but Luther was not able to?