In my studies I have keyed heavily on Church History. I love history and find great encouragement reading authors from every era of the post-Apostolic Church. At the same time, I am careful to keep such writings in their proper perspective. James Buchanan, writing specifically concerning the biblical doctrine of justification by faith alone, offers great clarity on keeping proper perspective concerning historical theology in the Church:
"The Post-Apostolic history of the doctrine (justification by faith) can only be derived from the writings of uninspired men: and there is a wide difference, therefore, between the Historical Theology of Scripture, and the Historical Theology of the Church. These writings, whether of ancient or modern date, possess no divine authority in matters of Faith, and their teaching on these subjects has no claim on our belief, except in so far as it can be proved to be in conformity with the unerring standard of God's Word."
I love Augustine, but he's not an Apostle. His works have to be scrutinized by Scripture. The same can be said about any of the church fathers, medieval theologians, and reformers. The same can be said about the modern era and her many pontificators...including good ole' Reep.