The culture of the Hellenic world means that a religion is not merely something to be lived: it also has to make sense. It has to work not only in practice, but in theory as well. Despite the passionate anti-Greek reaction of the Reformation, we are still, in this sense, all Greeks today. Take the doctrine of the Trinity, for example. Some people reject it because it sounds like polytheism. Instead, they make Jesus not God but something created by God – either a supremely favoured man or some kind of intermediate being. The Arians had such a view, and so does the Koran. Or they make Jesus only God, not man, relegating the intense humanity of the Passion to the status of a mere performance, a show put on by God through phantoms and angels rather than something utterly real and of eternal significance. Both these responses show a general feature of heresies, which is that they simplify the richness of orthodoxy and flatten it into a shadow of itself. “Simpler” may well mean “more easily acceptable”, but that is not the same as “true”. One could simplify quantum physics and get rid of its paradoxes until there is no metaphysical weirdness for anyone to object to – that might well make more people happy, but it would not be true.

  The three men we call “the Cappadocian Fathers” were active after the Council of Nicaea, working to formulate Trinitarian doctrine precisely and, in particular, to pin down the meaning and role of the least humanly comprehensible member of the Trinity, the Holy Spirit. St Basil of Caesarea, “St Basil the Great”, was the leader and organizer; Gregory of Nazianzus was the thinker, the orator, the poet, pushed into administrative and episcopal roles by circumstances and by Basil; and Gregory of Nyssa, Basil’s younger brother, although not a great stylist, was the most gifted of the three as a philosopher and theologian. Together, the Cappadocian Fathers hammered out the doctrine of the Trinity like blacksmiths forging a piece of metal by hammer-blows into its perfect, destined shape. They were champions – and successful champions – of orthodoxy against Arianism, a battle that had to be conducted as much on the worldly and political plane as on the philosophical and theological one. The sciences ought not to have to work like this, but all of them, at one time or other in their history, do.

  It is a relief to us as readers to note, after all this, that St Gregory of Nazianzus, as well as receiving the title of Doctor of the Church, is acknowledged as the most accomplished rhetorical stylist of the patristic age, and that this “style” does not adopt the over-ripe excesses of some late-imperial rhetoric (Augustine can get carried away in this direction sometimes, and Cassiodorus, in the sixth century, spends altogether too much of his time there). Gregory’s Second Readings do sound almost operatic at times, but the grandeur of the style does not exist for its own sake but comes from the splendour of its subject-matter. It is possible to be carried away by it, and enjoyable, even, to let that happen; but underlying the experience there is always a sense of being carried away in the direction of somewhere definite and somewhere worthwhile.