The De Trinitate is not the best known of St Augustine's works. But in my opinion it is his masterpiece, of a far greater doctrinal importance in the history of the Catholic faith than the Confessions or the City of God. It is indeed something of a theological portent, and as befits such a portent it took an uncommonly long time in coming to birth. As he himself says in a letter to the Bishop of Carthage which prefaces the work: ‘I was a young man when I began it, an old man when I had it published'. It seems that he began it about 400 A.D. Twelve years later it was still unfinished, and his friends getting impatient managed to publish the first eleven books of it and part of the twelfth, which was as far as he had got, without his consent. At this he stopped work on it altogether for some time, but was at length prevailed on to finish it— there are fifteen books of it in all—and publish it, perhaps round about 418 A.D.