This question, phrased in various ways, is a totally legitimate Pope Question that people ask, one that also falls definitively into the category of ‘Thesis Questions’. Why study Leo the Great? What makes Pope Leo I interesting?
First, I wanted to deal with the manuscripts and textual criticism of a fifth-century Latin text. So, apart from any intrinsic interest Leo holds, this was an overriding consideration when I decided to choose a topic — choose something that needs doing. And Leo I’s letters need doing, as one of my undergraduate proferssors pointed out to me.
Second, I’m also interested in the Council of Chalcedon of 451. I’ve translated its Definitio Fidei, after all. This event is a highly significant moment in the history of Christianity. To investigate Chalcedon is to end up looking not only into the history of Christology but also into the relationship between the imperial and ecclesiastical powers, the formation of the Oriental Orthodox churches, the relationship between Eastern and Western Christianity, the development of papal power/authority, the development of canon law. Since Leo helped orchestrate the whole thing, he once again fits the bill.
From the pragmatic angle of choosing something interesting that needs doing, these are really the reasons I chose Pope Leo I’s letters as the area of my dissertation’s investigation. From today’s vantage point, after three and a half years of research into Leo and the tradition of his manuscripts, I can give a much bigger, fuller, and broader answer as to why someone should study Leo the Great.
First of all, there is still inevitably his Christology, tied up the with Chalcedon issue above. There have been some recent monographs on Leo’s Christology, and they are good; they show the integrated nature of his thinking and some of his relationship with the prior Latin tradition as well as with the Greek tradition represented by St Cyril of Alexandria. There is, however, always more to be done, new angles to be approached, new techniques to be employed. His Christology is of far-reaching importance in Latin Christianity — Leonine hardliners actually went into schism with Rome over what they perceived as an abrogation of Chalcedon in the sixth-century Three Chapters Controversy, for example.
What makes Pope Leo ‘the Great’? Precisely his Christological teaching, primarily in The Tome, but also in the ‘Second’ Tome and a variety of sermons, not to mention scattered throughout his letters, both pastoral and dogmatic. Whatever the faults in his thinking that many modern scholars have plucked at, he is a massively influential figure in western theology, probably not only because he was a pope whose teaching was enshrined at what was perceived as an ecumenical council but also because he wrote so much less than guys like Augustine and Ambrose.
Remember, Christology ties itself into the centre of all Christian theology — how you formulate the nature(s), person, and work of Christ touches upon the Trinity and salvation, and, as Leo’s sermons show, Christian ethics. Leo is worth studying for this aspect alone.
Second, Pope Reasons. Leo is worth studying not just for his Christology but how he went about promoting it as well as his views on a variety of canonical matters. Leo is one of the first bishops of Rome to articulate a theory of the papacy, the heart of which is the Petrine primacy. And not only does he articulate it, he acts on it. Not always in a heavy-handed way, and probably because he thought he was right (that is, not out of personal gain) — thus his engineering of Chalcedon, but also his wide variety of letters to western bishops on matters of canon law.
Third, he is an important source for early western canon law. Leo the Great provides us with more letters than any other Bishop of Rome before Gregory the Great (590-604), and of these, more decretals. A decretal is, in later mediaeval and modern canonistic discourse, a papal letter with a universal binding force in canon law. I doubt Leo saw his quite that way, although he would certainly not have minded. They are letters about canon law and ordering of the church. Leo’s decretals touch on issues ranging from when to baptise people and whether to rebaptise people baptised by heretics (no) to the reconciliation of heretics with the church and whether monks can join the army (no). He addresses a lot of issues in canon law, and our earliest surviving collections of canon law documents include Leo.
His letters are compiled into great collections for canon law ranging up to 102 letters in one case, and throughout the Middle Ages, people use excerpts from Leo in their canonistic compendia — over 60 such compendia, in fact.
Finally, Leo’s letters are a valuable source for the human side of some events. Many stories are left untold by the historians, but hints and traces exist in these letters. For example, the Bishop of Narbonensis wrote to Leo asking what to do about people who lost Christian parents when very young and are now, as adults, uncertain as to whether they were baptised. Narbonensis had been invaded by Goths in 436 and the city of Narbonne besieged. Leo’s response to Rusticus of Narbonne reminds us of the human face of war and the war orphans of the fifth century. That is one example — I could give many.
Leo the Great was pope for the central two decades of the fifth century. He died 25 years before the deposition of the alst western Roman Emperor. His letters are important for our understanding of the Later Roman Empire, for our understanding of the church and its theology in that age, as well as for the culture and history of the time more broadly.
Why not study Leo the Great?