Very thorough and thoughtful historical survey of the development of orthodoxy and heresy. I appreciated this quote in which Brown expresses the fearful situation of this "post-Chalcedonian" age: "The threat of post-Chalcedonian theology is not that it teaches new heresies—those orthodoxy can resist—but that it is in the process not merely of abolishing the concept of heresy, but of forgetting that such a thing was important, or even that it ever existed."
Brown writes in the 1980's and so the end of this survey is abrupt and grim. He holds out the possibility for a resurgence of orthodoxy but makes cryptic connections to theology's collapse with the end of days. Thus, I believe him to be a bit pessimistic. If one were to take into account the last 40 years into his historical survey, despite the obvious declines, the spread of Christianity into the global south and the Neo-Calvinistic movement in the United States I think would serve to demonstrate that the days of Chalcedon are far from over. Not all descended from Israel are of Israel. The Lord always has a remnant among the heretics and this remnant if they are of the caliber of Nehemiah, are given sufficient grace to rebuild the walls of Jerusalem.
One final thought: Again, the irony of Brown's pessimistic final sections continues to strike me considering that during the time of publication, the orthodox theological ministries of R. C. Sproul, John Piper, John MacArthur, Doug Wilson, (and countless others) were in their early stages of faithfulness that begot the generations of Orthodox Christians we have today. May God grant us the grace of perseverance that we may hold fast to the faith once delivered to the saints.