In convening the prayer summit, Pope Benedict XVI is clearly reaffirming the ecumenical and interreligious outreach of his predecessor, Blessed John Paul II. But the German Pope has also marked out his own course, with modifications and additions that, in the Vatican's view, leave the event less open to misinterpretation.

For one thing, the participants will not pray together — at least, not in a formal fashion. They will gather at the end of the day for a moment of silence and testimonials to peace.

Although the border between prayer and reflection may be ambiguous in such encounters, it appears that Assisi 2011 will not repeat the formula of 1986, when representatives of each major religion offered a prayer at a final joint service.

Just as 25 years ago, participants will break off during the day for separate prayer services. But the difference is that this time around the prayers will be private moments in a cloistered monastery, not public performances throughout the town of Assisi.

In 1986, what generated the most interest among the media troops who went to Assisi were these very colourful and distinct forms of prayer, many of which took place inside Catholic places of worship. Buddhist monks chanted to the sound of a bronze gong. An animist from Ghana started a fire in a cup. A tribal chief from Togo invited spirits to enter a bowl of water. A native American "blessed" people on the head with eagle feathers.

For a few hours, Assisi seemed like a spiritual kaleidoscope, with clouds of smoke, sheep-hair amulets, tambourines and multi-coloured robes. And it left some critics with the impression that Christian and non-Christian elements were being mixed together inappropriately.

The program for this year's encounter appears designed to ensure that the private prayers will not have a public audience.

The third and perhaps most striking element of Pope Benedict's Assisi gathering is that four prominent non-believers will participate. The Vatican made a point of inviting them because, although they don't identify with any faith, they are seen as actively engaged in a debate over ethics, metaphysics and truth. That reflects the aim of the Vatican's new "Courtyard of the Gentiles" project, which seeks to promote discussions between Christians and non-believers around the world.

Cardinal Gianfranco Ravasi, president of the Pontifical Council for Culture, is co-ordinating the Vatican project. He will host a roundtable discussion in Rome with the four non-believers and Catholic intellectuals the day before the Assisi encounter. In Assisi, one of the four, Bulgarian philosopher and feminist Julia Kristeva, will speak at the main papal event.

This is a riskier dialogue gamble than the Vatican normally takes, but it does seem to reflect a priority of Pope Benedict. On his recent trip to Germany, the Pope shocked many listeners when he declared that agnostics who struggle with the question of God are closer to the kingdom of God than "routine" Catholics whose hearts are untouched by faith.

Ravasi said Oct. 14 that it was the Pope who had pushed to extend the Assisi invitation to non-believers.

A fourth difference between Assisi 1986 and Assisi 2011 has to do with its message to the wider world. In 1986, the focus was world peace; Pope John Paul called for a global truce that day, and many governments in conflict areas publicly supported the prayer summit.

Pope Benedict's agenda appears to be broader. The theme of the day is "Pilgrims of Truth, Pilgrims of Peace," and the Pope has said it should highlight believers' common responsibility to build a society based on truth. Part of that task, he recently told Muslim representatives, involves protection of the family based on marriage, respect for life in every phase of its natural course and the promotion of greater social justice.

It would be surprising if these issues do not surface at the Assisi gathering given Pope Benedict's insistence that true peace-building is a "constant struggle against evil" and not merely negotiations between parties in conflict.

The Pope will give two main talks in Assisi — at the beginning and end of the day — and the program calls for talks by several of the non-Catholic participants as well. But as with many of Pope Benedict's events, there will also be several moments of silence: following a simple meal in the style of St. Francis, at the lighting of lamps at sunset and in individual prayers before St. Francis' tomb.

Repeating a gesture of Pope John Paul for the second Assisi prayer gathering in 2002, Pope Benedict will escort his guests to Assisi on a train that departs the Vatican in the morning and returns at night. Like the rest of the day, the train trip is expected to be less a socializing moment than an occasion for prayer and meditation.