So, how do we use scripture to identify what is scripture? If we say it's based on when other books refer to the specific books, then why are letters of Paul missing and why are some Old Testament books never quoted and Protestants removing books that Christ and the apostles quoted from?
Then again, how do we prove the scripturehood of the latest book, being Revelation? If it's not scripture, then any book or author John refers to might not be scripture, and then any books they refer to might not be scripture.
Never is the Scripture said to be THE guidebook of the Church. They are the center of Tradition, but they are still Tradition (II Thessalonians 2:15). The reason we know what is scripture is because of the Canons of the Church, which are Tradition. Protestants just pick and choose scripture buffet style. The Scripture was changed by Luther, who wanted to disclude James because he couldn't make it work with his doctrinal beliefs.