In the 370s a great complex of buildings was being created around the city of Caesarea in Cappadocia. There were hospices for the sick, asylums for lepers, hostels for visitors, nurses and physicians and a grander building for the supervisor and his supporting clergy.

The inspiration for the project was the bishop of the city, Basil, a man of immense energy who left his mark as an administrator, ascetic, theologian and founder of a monastic rule still influential in the Orthodox churches. On his death in 379, his friend and fellow Cappadocian Gregory of Nazianzus delivered a wonderful funeral oration in his memory. When Gregory spoke of the leper complex, he went through the other wonders of the world, including the Pyramids, the walls of Babylon, the Colossus of Rhodes and the mausoleum at Halicarnassus. These, he said, had been put up only for the fame of their builders. Basil’s achievement was greater than these as it was a stepping stone to salvation in Heaven.

Basil, Basil’s brother, Gregory of Nyssa, and Gregory of Nazianzus, “the Cappadocian Fathers” as they are known, were born in an age when well-born Greeks enjoyed the finest education. The aim of a lengthy curriculum with a personal teacher in one of the great cities of the ancient world — for Basil and his brother this was Athens — was paideia, the profound absorption of Greek culture culminating in the mastery of rhetoric. The ability to persuade others through speech was intrinsic to success in life, not least in arguing one’s city’s cause before the emperor. The skill transferred into the Church and the sermons and funeral orations of the period still make impressive reading. Augustine was the city orator in Milan before his conversion.

When Basil turned his own thoughts to the education of young Christians, he wanted much the same for them as he had enjoyed in Athens, a city “truly of gold and patroness of all that is good”. In his Address to Young Men on the Right Use of Greek Literature he argued for a grounding in classical writings. “Just as dyers prepare the cloth before they apply the dye, so must we also, if we would preserve indelible the idea of the true virtue, become first initiated in the pagan lore, then at length give special heed to the sacred and divine teachings, even as we first accustom ourselves to the sun’s reflection in the water, and then become able to turn our eyes upon the very sun itself.”

The result is intellectual breadth and clarity of thought. The treatises of the 4th-century theologians are far from the weighty and impenetrable texts that one might expect. In his works, Gregory of Nazianzus included quotations from more than 1,000 years of literature, starting with Homer, taking in the historians Herodotus and Thucydides, the philosophers Heraclitus, Plato and Aristotle and even the Jewish Philo and, from a century before, the philosopher and historian Plutarch. There is a fine passage in his Second Theological Oration (often listed as Oration 28), delivered in Constantinople in 380, in which Gregory meditates on the mysteries of life, how the human mind can focus on itself but still imagine the Universe, how sound is produced by our vocal organs but then heard and understood by another, what brings children and parents so close together. If we cannot understand such mysteries, he concludes, how much harder is it to understand the mystery of God?

Of course, this was an elitist and often arrogant group. Gregory of Nazianzus was furious when Basil asked him to become bishop of the obscure town of Sasima. “An utterly dreadful, pokey little hole, a place wholly devoid of water, vegetation and the company of gentlemen” was his contemptuous response. Debates were often rough. Academics and bloggers today who display their fragile egos and vitriolic pens at the first hint of criticism have nothing to learn from their 4th-century predecessors. Yet their achievement was to create theological discussion at the very highest level.

We know of the works of the Cappadocian Fathers as they developed a terminology in support of the Trinity and have been honoured for this in the Orthodox Christian tradition. However, there are other, now mostly forgotten, intellectuals who argued with as much intensity on the other side of the question. Eunomius, another Cappadocian, but of more humble background, made himself the target of the Fathers by the relentless way in which he used logic to clarify theological issues, arguing that it was the distinction between Father and Son that mattered, not the “one in substance” of the Trinitarians. He was taunted for having the philosopher Aristotle as his bishop and inspired a rush of responses “contra Eunomium” — against Eunomius.

This fertile tradition of debate was infused by the richness of pagan thought but not diminished by it. It faded at the end of the century, largely through the legislation of the emperor Theodosius I (379-95). The Eunomians and those who believed Jesus had seen himself as subordinate to the Father were declared heretical by law and pagans were silenced. A great deal was lost.

I am not a theologian but I do try to read some theology to understand the issues in contemporary debate. All too often I get stuck on sentences that mean nothing even on the third or fourth reading. As a historian I am often frustrated to be told that there is only one historical explanation for a supernatural event when the evidence is insufficient to support any at all. I have seen theologians taken to task for a wholly inappropriate use of logic. Very often theologians seem unaware of how weak their arguments are to anyone with a philosophical background. It is then that I think of the wisdom and confidence of Basil of Caesarea. His broad training in “profane” subjects served only to enrich his theology and strengthen his arguments and did nothing to diminish his Christian compassion.

A New History of Early Christianity by Charles Freeman is published by Yale University Press, £25