Southern was born in Newcastle-upon-Tyne on 8 February 1912, and educated at the Royal Grammar School, Newcastle, and at Balliol College, Oxford, where he graduated with a first-class honours degree in history.
His son, Dr Peter Campbell David Southern, was Head Master of Bancroft's School and Christ's Hospital.
[3] Southern is one of 20 medieval scholars profiled in Norman Cantor's Inventing the Middle Ages: The Lives, Works and Ideas of the Great Medievalists of the Twentieth Century.
This pioneering work, sketching the main personalities and cultural influences that shaped the character of Western Europe from the late tenth to the early thirteenth century and describing the development of social, political, and religious institutions, opened up new vistas in medieval history, and has been translated into many languages.
The final chapter of the book (a chapter dedicated to spirituality) has often been credited with helping to popularize the thesis that in the 11th century Anselm of Canterbury "was the founder of the new type of ardent and effusive self-disclosure", epitomizing a broader tendency to "a greater measure of solitude, of introspection, and self-knowledge" that "ran like fire through Europe in the generation after his death and produced an outburst of meditations and spiritual soliloquies".
[4] Southern's ideas were seminal for generations of scholars of medieval spirituality, helping them to build a picture of what they called affective piety – emotionally charged prayer and meditation mostly focused on the Passion of Christ.
Southern argued that scholars in the 19th and early 20th centuries had built the "School of Chartres" into a romanticised edifice out of all proportion with the documentary record.