The Fathers of the Church is a term applied to the great Christian writers of the centuries following the apostolic age. The fathers may not be well-known, but, thanks to them, the church survived in an age of persecution and established the basic beliefs of Christians, such as one God and Jesus as redeemer of the world.

They also established much of our ecclesial terminology, such as “sacrament” and “Trinity,” words not found in the New Testament.

They also gave us the New Testament and thus the complete Christian Bible.

The first Christians had the Hebrew Bible (the Old Testament) as a source of written revelation, but many wondered about some of the books written by Christians, such as the letters of the apostle Paul and those four books about Jesus, called “Gospels,” or “the good news.”

The Fathers of the Church worked out a theology to use those later books with the same reverence and authority given the Old Testament.

As early as the second century some fathers had created canon lists of Christian books that belonged in the biblical canon. In 367 the great theologian Athanasius of Alexandria settled matters when he proposed a list of 27 books to be considered inspired, which we now know as the New Testament.

Almost all of the fathers were priests or bishops, and their main pastoral concern — a little surprising to us — was preaching. As usual, there were endless topics for consideration, but the fathers focused endlessly on the biblical text — and for good reason.

Christianity was, like Judaism, a religion of the book, but almost no one could read. Believers learned about the Bible from the many sermons that they heard about the scriptural text. Often the interpretation was linked to a theological issue, such as the Nativity and the Incarnation.

The ancient Jews were aniconic, that is, they thought it a sin to make images of people. But the fathers, mostly Greek and Roman, thought images would help people understand the text better, and some early Christian churches, such as Ravenna, Italy, have stunning mosaics showing Jesus, his family, his disciples and many events in his life.

These brought an immediacy but also a familiarity to the biblical text.

Yet might the New Testament obscure the Old? Not at all, because the fathers demonstrated the close relation between the two.

For example, what could the Red Sea escape mean to Christians? The fathers said, that like the Hebrews, before baptism the Christians were slaves, not to a person but to sin, but when they passed through the water (baptism was by immersion), they emerged from the water free people.

Finally, the fathers read the Bible “in the church,” that is, they understood Scripture as the church’s book and saw no contradiction between biblical and ecclesiastical teaching, still a valuable lesson.

We modern believers owe the fathers an incalculable debt.

(Joseph F. Kelly is retired professor at John Carroll University in University Heights, Ohio.)