"Scripture is only known by the authority of the church"Now there's a sentence that can mean different things.
If I take that to mean "Scripture is known because the church has witnessed to the authority of these writings from the beginning" I'd agree.
If I take that to mean "Scripture is known because an official decree was made several hundred years after Christ when the list of books was finally made which fully agrees with what the (western) church uses today" -- then I'd disagree.
On what grounds would I disagree? On the grounds that the church is "built upon prophets and apostles, with Christ Jesus Himself the chief cornerstone." (Or to support the same thing another way, based on apostolic succession back to the original apostles.) This has direct implications for whether the church has any authority to decide over certain books. The church did not have the authority to decide whether to include the accounts of Christ's life and teachings, and the church in the earliest days of her written works recognized four such accounts of Christ's life and teachings (Matthew, Mark, Luke, and John). The church did not have the authority to decide whether to include the prophets. And (at the risk of being repetitive) the church did not have the authority to decide whether or not to include the writings known to trace to the apostles. On the matter of the prophets and apostles and especially that of Christ, there was no authority to do otherwise than recognize, accept, and proclaim them.
The early church records show that the writings of the prophets and apostles and the gospels of Christ's life had fully gained recognized authority centuries before any council recognized them, and they gained this authority based on what they were. This recognized authority, long predating any such councils, extended to all of the books in the (Protestant) Old Testament and the large majority of the books in the New Testament. Any council which had not recognized those books would have been illegitimate.
Why would a council be illegitimate if it had not recognized those books? Because the church cannot have authority to deny its own foundation. Because the church is "built upon prophets and apostles with Christ Jesus himself the chief cornerstone", the church is bound by what it is and by what those writings are to recognize the authority of those writings. A church which denied the writings of the apostles would not have been apostolic. And, to put it more strongly, a church which took upon itself to decide whether or not to include the writings of the apostles would not have been apostolic either. The records show that the books known to be apostolic were in fact received without dispute; and in this way the church was established and confirmed as apostolic.
The only authority the church exercised was over the (relatively fewer) disputed books. For the disputed books, the church had to to discern which ones had ancient records strong enough to be officially recognized. In some cases this meant trying to determine whether a certain writing did in fact come from an apostle or contain the teachings of an apostle. This ruling over disputed books was a useful function, and the western churches have all followed a fairly unified canon of Scripture for many centuries now.
Biblical scholarship in recent centuries has made the attempt (in its own way) to re-open the question of the canon. They have discovered that Matthew, Mark, Luke, and John are a better source for the life of Christ than the faddishly fashionable but historically worthless "lost gospels". They vindicate the church's hesitancy towards other books such as 2 Peter and Revelation which gained acceptance more slowly. The scholars' arguments have sometimes mirrored the ancient disputes. It shows that the early church did a faithful job in recognizing what she was constrained to recognize and in carefully considering the remaining disputes.
But as for the disputed books ... it's a little bit like buying a car. You can argue about whether to get power windows or a fancy speaker system installed in the car. But you cannot opt out of having tires, transmission, and an engine or it's just not a car. In the same way the church decided on the disputed books, but could not have decided otherwise on the books of the prophets or the apostles or the four anciently attested gospels.