"To be deep in history"

“A second problem has to do with our ‘reading’ of church history. Often we speak of our unity during the first millennium. But such appeals to history can be misleading or even dangerous. We all know the old adage, that you can prove anything by Scripture. Much the same could be said of church history. Both the 19th-century papal initiatives vis-à-vis the East and the Eastern responses to these initiatives appealed to the undivided Church of the first millennium, or the Church of the seven ecumenical councils, but they drew from the historical record very different conclusions. We still face the same problem today. Should more weight be given to Leo the Great’s legates at the Council of Chalcedon, who referred to him as universalis papa, or to Gregory the Great, who pointedly objected when Eulogius of Alexandria referred to him as universalis papa? Should we regard as particularly significant the fact that St. John Chrysostom appealed to Pope Innocent of Rome after his deposition from the see of Constantinople, or should we also take into account the fact that he appealed as well to Venerius of Milan and Chromatius of Aquilea?”

http://www.svots.edu/Faculty/John-Erickson/articles/canon-28-english.html/