To reject [the development of doctrine with regard to Mt. 16 and the papacy] on the argument that it was a development and that development was in itself unacceptable made it difficult for the biblical exegesis of the Reformation and post-Reformation periods to contend with those on the left wing of the Reformation who, sharing the insistence of the 'magisterial Reformers' on the sole authority of Scripture, rejected the reliance on trinitarian doctrine of Nicaea as a necessary presupposition and method for reading biblical texts.Just so. You can't have it both ways: to reject doctrinal development when it is unpleasant to you, and to accept it when it satisfies you. Even less helpful is to reject it entirely: for then you have no reasonable grounds for condemning those who use the principle of letting Scripture interpret Scripture in ways that you don't like, either. In the end such an approach reduces hermeneutics to a matter of personal taste: "I'll have a Trinity Cola" becomes, in the end, a matter of preference like others' predilection for Arian milkshakes. It's a poor foundation for the truth.
For having thus developed out of Scripture, the trinitarian perspective had in turn become a way - or rather, the way - of interpreting Scripture. As it was systematized at least for the West chiefly by Augustine, this method of biblical exegesis was cast in the form of a 'canonical rule (canonica regula)'...[A]ny passages that, taken as they stood, appeared to contradict church doctrine were subject to the 'canonical rule' and required careful handling...If the Protestant Reformers and their descendants were willing to hold still for such a manipulation of New Testament passages in the interest of upholding such a doctrinal development that had come only in later centuries - and they were - what stood in the way of such manipulation when the passage was 'This is my body' or 'Thou art Peter, and upon this rock I will build my church'? [p10f.; emphasis in original]
If the gates of hell do not prevail against the Church (and they don't), then our attitude ought to be more like this: "This passage of the Bible seems to me to say [X], but that would be contrary to what the Church has always taught. I must be mistaken, because the Church can never be." To say this demands that we possess and exercise the virtue of humility.