What we are trying to get to the core of is exactly why sola-scripturists believe that the 27 books of the NT are inspired.
Did you go through all the competing gospels/letters that existed during the first 5 centuries and eliminate them one by one just to make sure? Have you read any of the the other books that were rejected by the Church? Maybe the Church got it wrong. Maybe there was a wide-spread conspiricary to cover up the true message of Christ by the church. If they were corrupt in some areas, why couldn't they have failed you in canonizing scripture as well? Perhaps there is authentic scripture that once existed, but has been burned by the church so that no record longer exists. You may never know. Maybe God sent another prophet (joseph smith)? because the church got corrupted? At the end of the day,if you want to be a bible believing Christian, you have to trust the churches decision (that is, have faith in the church) that they kept the right books, and rejected the wrong books, even if you reject some of their doctrines.
Does this seem like an arbitrary pick and choose scenario, or is it just me?