Despite his vast output, St Augustine completed only one commentary on a whole book of the Bible: the Expositio epistolae ad Galatas, written circa AD 395. This work enjoyed understandable success in the Middle Ages and beyond: over 60 manuscripts survive from the 8th to 15th centuries. Eric Plumer's 2003 bilingual, commented edition of the Expositio in Oxford Early Christian Studies bears witness to ongoing interest in this brief but pungent exposition of St. Augustine's early views on grace and on its unfolding in history.
However, following the critical edition of the commentary in vol. 84 of CSEL in 1971, and Jean Rousselet's subsequent review article, work on the text of the commentary has ground to a halt. I shall argue that there is a compelling need for a new edition of the text: the manuscript basis used for CSEL 84 is too narrow, the editor's collations are inaccurate, and the manuscript families he identified need to be questioned.
I shall then sketch out how a new edition may be prepared, based on the previous editions, on new collations, and on information gathered from my recent edition of a text that sometimes travelled with the commentary on Galatians, namely St Augustine's unfinished commentary on Romans. I shall here address that most distressing methodological problem for all editors of texts with large traditions: do we have to collate all the manuscripts, and if not, how do we choose?