St Augustine has been the most influential single voice in the history of western Christianity. Those in quest of a new theology often find it necessary to begin by criticizing him. This is fair enough; but a Christianity conscious of its past cannot discard him. This is clear in ecumenical dialogue with the Churches of the Reformation: their theology is hugely indebted to Augustine, and dialogue between them and Catholics must often return to him as their common source. Augustine lived in an age, like our own, where Christian values were not dominant in society, and where a Christian active in society had to show readiness to compromise in order to maximize the common good. To this we can relate his teaching on sexuality, where he accepted that the Church had to tolerate sexual behaviour within marriage that did not satisfy the strict letter of Christian morality but was often necessary for marital harmony. Here again was an area where the Church had to recognize a secular sphere with its own character and needs. Augustine's teaching on the prime importance of harmony in society went together with a lack of belief in human progress that contrasts sharply with the recent teaching of Gaudium et spes; but it is the latter that, fifty years after the Council, begins to look dated. The Church must maintain a constant dialogue with tradition. Within that tradition Augustine's place cannot be contested.