Light is an essential element in our celebration of Christmas, from the dazzling sparkle of the Christmas tree and the illuminated displays on the High Street to the flickering flames on the Christmas pudding. But what makes light so important to our most popular and, for Christians, arguably most religiously significant festival? The answer lies not just in the traditions and rites of Christianity, but in the beliefs and festivals of pre-Christian Europe that Christianity inherited, adopted and reinterpreted.
In Europe, long before the Christian church placed the celebration of the birth of Christ at the end of the year, midwinter was a time for rituals, feasting and conviviality. But why feast and be merry at the most miserable time of the year, when the ground is frozen and few crops grow? G.K.Chesterton pointed to this paradox when he wrote that man chooses to be joyful "when the whole material universe is most sad", and perhaps we can see it as an act of defiance of the elements.
A more practical explanation is that most of the cattle could not be kept alive during winter and would therefore be killed before the end of the year, giving an excuse for a last great feast before the most severe weather arrived.
But to get to the heart of the old pagan festivals we have to understand their religious purpose. They were an affirmation of humanity's relationship with the forces of nature and the belief that they could be placated and encouraged.
The old winter festivals expressed fear and hope and were about ends and beginnings and death and life. They dramatised the death of the old year and the birth of the new, which are symbolised even today by personifications of the old year as an old man and the new year as an infant.
At a time when the sun appeared to be in decline, the celebrations were attempts to propitiate the forces of nature that were responsible for the coming of the bleak season and to encourage the return of the life-giving sun and fertility. Lights and fires were important aspects of these festivals for they were seen to encourage the return of the sun. Evergreens were used as decorations to symbolise the continuity and perseverance of life at a time when other trees and plants were dead.
These elements were present in the customs of southern Europe and the Yule of the Teutonic north. Light was, understandably, even more central to Yuletide than to the Roman feasts of Saturnalia and the Kalends, for not only were northern midwinter nights long but the season was supposed to liberate ghosts and demons. The more light there was the better it helped to keep away the spirits, as one sat beside the warmth of the burning yule log while monsters such as the Julebukk roamed the dark outside.
The Kalends of the later Roman Empire ended with the birthday of the Unconquered Sun on 25 December, which was also the feast day of the Mithraic religion, one of the "mystery religions" of the Empire. Again we can see the importance of continuity, light, birth and rebirth in the idea of the sun as unconquered. Early Christians did not celebrate the birth of Christ and the Gospels gave no date for His true birthday. But if it was convenient it was also apposite that, in the 4th century, the church decided to adopt 25 December as the date.
Associating the traditions of midwinter festivals and the source of light and its rebirth with the birth of the son of God ensured that Christmas embraced and embodied many pre-Christian customs. Our modern festival has been, since the introduction of electricity, remarkably well lit. In recent years, even the outside of houses has been illuminated, with lights enfolding them and some of the season's iconic images, such as reindeer, lit up on the roof. Father Christmas is sometimes featured, too: a sprawling figure in red, captured mid-climb on his way towards the chimney. (Rising electricity bills rather than any newly acquired sense of aesthetics are likely, however, to discourage these efforts.)
All the world's great religions have shared a concern for the passage of the seasons, the need for fertility and a preoccupation with the passage of time, dark and light, ends and beginnings. Some sects and cults have been less worried about the end of the year than the end of the world and, rather than searching for renewal with the aid of prayers, rites, light and greenery, have instead awaited the apocalypse.
Archaeologists recently discovered scripts from the once great Mayan religion prophesying that the world will end on 21 December 2012 - just a week away. But before you go wild with your credit cards it might be well to take note that other experts think the inscriptions refer not to the end of the world but to the start of a new era. If we light some candles, it might help.
A.W.Purdue is a former reader in British history at the Open University. He is now a visiting professor of history at the Northumbria University and visiting reader at the OU.
J.M.Golby and A.W.Purdue, The Making of the Modern Christmas (The History Press, 2000).
Key stage 1: Let there be light ... and toys
Miss_wilson's Year 1 plan is packed with festive activities. It covers light and science, festivals of light and toys - perfect for the Christmas season. bit.lyFestivePlan
Key stage 2: Christmas everywhere
Explore how Christmas is celebrated across the globe with kirstynutton2003's scheme of work. bit.lyWorldofChristmas
Key stage 3: Christian Christmas
Explain what the festive season means to Christians with this lesson pack from TES partner TrueTube. bit.lyChristianChristmas
Key stage 4: A Christmas Carol
Try S Oup's GCSE resource pack to prepare pupils for an assessment on the seasonal tale. bit.lyChristmasCarolStudyPack.