This book is made up of four lectures delivered at the Queen's University, Belfast, under the aegis of the Wiles Trust. They are printed much as they were delivered, with some slight re-arrangement and the verbal alterations needed when the spoken word is transformed into the written word. One of the features of the Wiles Lectureship is that scholars interested in the subject of the lectures are invited not only to attend them but promptly to criticize what the lecturer has said. I have profited from that salutary experience and have made a few further emendations in my text.

The nature of my subject precludes startling original research. It has, rather, been my aim to try to correlate and to put into perspective the intellectual achievements of the last two centuries of the Byzantine Empire, when the State was collapsing but learning never shone more brightly. I have made one serious omission. It would have taken too much time and space to have included a worthy discussion of the art that was the most splendid achievement of the period. The product of Byzantine scholars is less attractive to us today than the product of Byzantine artists. But scholarship should be judged by the standards of its age, not by the tastes of subsequent generations.

I have to confess that I have not read every word of the works of scholarship about which I am writing. That would be the task of a lifetime, especially as many of them are unpublished and not easily accessible nor easily legible. I am dependent for my knowledge of them to the labours of scholars who have studied them.