All Souls: When the saints come marching in ...

At this time of year, avoid churchyards and don't look at your shadow ... Paul Vallely on the significance of All Hallows Day.

This is the season of the dead. All around the world, at the beginning of November, local customs recall that at this time many thought the supernatural held sway upon the earth. The notion, prompted as it is by the winter equinox, ought to be confined to the cultures of the northern hemisphere. But thanks to the influence of the Catholic Church, the wall between the earth and the heavens is breached this weekend all across the globe.

In many cultures the imagery for this is now primarily Christian. The first of November is All Saints' Day (or All Hallow's Day) when the church celebrates the lives of martyrs and others who led heroic gospel-inspired lives. It dates back to the second century when Christians would hold eucharistic services at martyrs' tombs "in memory of those athletes who have gone before, and to train and make ready those who are to come hereafter," as one second-century writer put it. Originally it was held on the Friday after Easter, but in the ninth century it was moved to November.

It struck new resonance there. Among pre-Christian cultures, such as the Celts, winter began on 1 November, when tradition had it that the sun itself entered the gates of hell and allowed evil spirits into the world for 48 hours. The Church, which was adept at appropriating pagan festivals, covered this extended period by making 2 November a day when the faithful pray that all those who have died should be released from purgatory, the place where souls are purged of their sins before they pass into heaven. It is called All Souls' Day, while the night before All Hallows, Hallowe'en, was once a Church vigil too, until Rome suppressed the practice as recently as 1955.

All around the world old superstitions cling to the season. The souls of the dead return at this time to their hearths to warm themselves, so it is as well to take measures to keep spirits at bay. Traditional advice was to avoid churchyards, not look behind at sounds in the night, to avert your eyes from your shadow in the moonlight and refrain from hunting for fear of wounding a wandering spirit. Other traditions centred around prophecy - often to find the identity of a future spouse - which was easier at this time when the veil between the overworld and the underworld was briefly lifted.

Certain of pagan traditions were transferred to local saints. It was only in 1234 that Rome arrogated to itself the power to veto the creation of new saints. Before then the local bishop could approve them. Each locality had its own saints who dominated the Catholic imagination in medieval times. The veneration of saints was one of the things Luther and the Protestant reformers objected to, arguing that prayers to saints detracted from the status of Christ as the mediator between God and humanity.

Of course, we are all saints now. The tragic circumstances of her death were sufficient to have Princess Diana widely proclaimed to have joined Mother Teresa in heaven. St Paul might have approved - he used the word as a synonym for a Christian - though more modern theologians might object. But there was in the response to her death a hint that, even in an age of rationalism, an echo lingers of the old feelings about the interstice between life and death, between reason and faith. Behind the quaint carnivals of the season there still lurks the suspicion that there may be more to heaven and earth than are dreamt of in our philosophy.