Over the past 2,000 years, Christianity has played a vital role in Western culture. Art, science, music, architecture and literature have drawn on religion to such an extent that Christianity has formed many of our cultural ideas, symbols, rituals and political ideals. The Irish theologian, Prof Richard Hanson, has pointed out: "As a religion, Christianity has both formed history and has been formed by history."

Christianity has always had good reason to emphasise the study of its own history. "The Christian religion, above all others, is concerned with the relationship of time and eternity," Sir Steven Runciman of Cambridge has written. "Its central doctrine, the Incarnation, is not only an eternal truth but an event in history; it is a bridge between the temporal and the eternal."

Christianity claims to have originated in a series of historical events which, to varying degrees, are normative for its message and its significance. The study of Christianity could never be limited to the study of the Bible and the life of Christ alone.

The Church decided which books were canonical - or part of the Bible - and which books to exclude from the tradition. As the Church of Ireland Bishop, Most Rev Richard Clarke, has pointed out, "there is a very important sense in which [Christ] did not found the Church". Jesus preached the Kingdom of God, and the Church was founded on His teachings.

The Bible and tradition run parallel with the story of the Church in shaping Christian experience. And so, the story of Christianity over the past 2,000 years is not only another branch of history, but an important component in theology. According to Prof Runciman, church history needs objective study, intuitive sympathy, imaginative perception, and a comprehension of "the fears and aspirations and convictions that have moved past generations". Traditionally, the history of Christianity has focused on saints and missionaries, rather than providing an independent interpretation of religious behaviour. This apologetic tendency was strengthened in the middle of the 20th century by theologians who wrote as though human history had no meaning at all after the death and Resurrection of Jesus Christ.

Today, no Church historian would seek to justify many of the experiences of past generations in the Church. Who would seek to defend the Crusades, the Inquisition or those Christians whose anti-Semitism was a constituent part of the political culture and climate leading to the Holocaust? Church history seeks to place these events in their context and to understand the contribution of other forces and the social, political, economic and cultural circumstances of the times.

It becomes more difficult to appreciate the contexts of events closer to our own lives. Will future generations see the missionaries of the last century as enlightened advocates of the social gospel, seeking to combat the worst extremes of imperial exploitation and indigenous superstition, or as agents of colonialism? Will future generations looking at 20th-century South Africa judge the Churches for their resistance to apartheid, or the contribution of the Dutch Reformed Churches to formulating apartheid? Will future historians looking at the Irish church in the 20th century emphasise the growth of the ecumenical movement, or sectarian bigotry?

Throughout this year, as we take stock of 2,000 years of Christianity, this series will attempt to take us through the conversion of the Roman empire and the formulation of Christian doctrine; the expansion of Christianity - often thanks to the journeys of Irish missionaries; the great schism that divided Christendom, East and West; the rise of Islam, the Crusades, and the collapse of the Byzantine Empire; the invention of movable type and the translation of the Bible; Luther, Calvin, the Reformation, the Counter Reformation and the Renaissance; the Pilgrim Fathers and the move to guarantee religious freedom and the separate church and state; the growth of the modern missionary movement and the abolition of slavery through the energy of evangelicals; the challenge to faith posed by Darwin, Marx, Nietzsche and Freud; the murder of six million Jews in the Holocaust; and the 1960s, when Pope John XXIII convened Vatican II and Martin Luther King led the Civil Rights Movement.

The 1960s also saw the Church and theology challenged by the concepts of the "Death of God" and "post-Christianity". By the end of the 20th century, we reach a Church that continues to grow phenomenally in the TwoThirds world, reinvigorated in part by liberation theologies, but challenged by a resurgent Islam. But in the older Christian heartlands, were liturgical reform and debates about ethics, sexual morality and the ordination of women signs of a church that was finding new life and renewing itself, and was the Church capable of confronting decline and secularism?

Patrick Comerford is a writer on church history and theology. Contact: theology@ireland.com

2000 AD next appears on Monday February 28th