The Irish Steyler missionary Vincent Twomey received his doctorate from the University of Regensburg in 1978 with the thesis "Apostolikos Thronos", supervised by Joseph Ratzinger. The work, originally published by Aschendorff, has now been published in a revised version by the University of Steubenville.

Twomey, who belongs to Ratzinger's circle of students, is one of the most widely respected and accomplished theologians of our time, not least because of his historical knowledge. His dissertation has rightly been reprinted because it contains fundamental insights into church doctrine in the 4th century. After the end of the persecutions and the dawn of the Constantinian era, the 4th century is the time of fundamental reflections on the place of the church in this world.

Twomey has succeeded in identifying two decisive phases in the "Church History" of Eusebius of Caesarea, which was published several times: the first, pre-Constantinian edition of his Church History still emphasises the apostolic character of the Church in a very traditional way. The basic principle is episcopal succession, which brings together the great apostolic-Petrine bishoprics of Alexandria, Antioch and Rome.

Eusebius then mutates into an imperial court theologian. He opportunistically became a mouthpiece of imperial Constantinian ecclesiology, i.e. political theology. As a result, Constantine's successors experienced an Arian crisis, a theology adapted to the political circumstances.

This in turn brought the Alexandrian bishop Athanasius onto the scene. Athanasius turned against the political theology of the "imperial bishops" in favour of apostolic ecclesiology and thus church freedom. In doing so, Athanasius was particularly close to the popes in Rome.

The topicality of the question is unmistakable: apostolic tradition or political opportunism?