The Bogomils: A Study in Balkan Neo-Manichaeism (Obolensky, Cambridge, 1948)

Dimitri Obolensky was a historian of the medieval Slavic and Byzantine world at Oxford. This 1948 monograph, from his Cambridge doctoral research, is the founding modern study of Bogomilism, setting the movement within the wider history of Balkan and Byzantine dualism and following it from tenth century Bulgaria into the Byzantine Empire. Like every later account, it rests heavily on the writings of the movement's Orthodox opponents, chiefly Cosmas the Priest's tenth century Sermon Against the Heretics and Euthymius Zigabenus's twelfth century Panoplia Dogmatica, since no Bogomil text of their own survives; Obolensky reads these hostile witnesses critically rather than at face value, but the limit is the field's own and not this book's alone.