"But here some one perhaps will ask, Since the canon of Scripture is complete, and sufficient of itself for everything, and more than sufficient, what need is there to join with it the authority of the Church's interpretation? For this reason,—because, owing to the depth of Holy Scripture, all do not accept it in one and the same sense, but one understands its words in one way, another in another; so that it seems to be capable of as many interpretations as there are interpreters. For Novatian expounds it one way, Sabellius another, Donatus another, Arius, Eunomius, Macedonius, another, Photinus, Apollinaris, Priscillian, another, Iovinian, Pelagius, Celestius, another, lastly, Nestorius another. Therefore, it is very necessary, on account of so great intricacies of such various error, that the rule for the right understanding of the prophets and apostles should be framed in accordance with the standard of Ecclesiastical and Catholic interpretation.I'm not trying to say this means that the Catholic church today in the 21st century led by Pope Benedict XVI is THE only church, as the Eastern Orthdox could read this quote without a problem. You have to remember that at the time, EVERY orthodox christian church was one, the Catholic church, and then it subsequently split. So the Anglicans and Orthodox and Lutherans today all come from this original Catholic church, we would all be Catholics back then, and this is all of our heritage. So we don't simply default to the modern Catholic church because there is the same word used, which means Universal, or According to the whole. It is still an argument of who are the true Catholics. Presbyterians think they are, and Lutherans think they are, and modern Roman Catholics think they are.
Moreover, in the Catholic Church itself, all possible care must be taken, that we hold that faith which has been believed everywhere, always, by all. For that is truly and in the strictest sense "Catholic," which, as the name itself and the reason of the thing declare, comprehends all universally. This rule we shall observe if we follow universality, antiquity, consent. We shall follow universality if we confess that one faith to be true, which the whole Church throughout the world confesses; antiquity, if we in no wise depart from those interpretations which it is manifest were notoriously held by our holy ancestors and fathers; consent, in like manner, if in antiquity itself we adhere to the consentient definitions and determinations of all, or at the least of almost all priests and doctors."
But this is an interesting quote from church tradition that scripture is to be interpretted by the church as a whole. This slaps Congregationalism in the face as well as SOME interpretations of 'priesthood of all believers'. But for those international denominations and churches who decide what scripture means, through tradition, still have a fighting chance.
What I take from St. Vincent's quote is this: Scripture is the Word of God, however it must be interpretted, and it is interpretted through Tradition. Tradition is that which has been believed by all, everywhere, always. This is why the church as a whole must search through tradition and examine what scripture means.
I think the Orthodox are correct in that we cannot understand more about Christianity than the apostles did at the time. Of course the debate now is about what the apostles believed. And that is why we need Tradition.