My two posts are:
"Day of reflection, dialogue and prayer for peace and justice in the world"
Assisi Three and the question of multireligious prayer
A recent report at news.va - Pilgrims of Truth, Pilgrims of Peace - gives an updated view of the event due to take place next week. It is interesting to see the different Vatican dicasteries that have been involved in preparing the Day.
For the first time there will also be a number of non-believers invited by the Pontifical council for Culture – undersecretary of the council, Mgr Melchior Sanchez de Toca explains why: "It was this Pope's desire to invite some people, non-believers or at least who do not belong to any particular confession or religion.......It may seem a contradiction, but you can find sometimes in non-believing people a spirituality which can help us to examine ourselves and grow in our spirituality"The invitation extended to atheist philosophers is an aspect of the "courtyard of the gentiles" initiative. Reports indicate that one of the invitees has withdrawn, though this appears to be more to do with the nature of the particular event in Assisi rather than hostility towards dialogue with the Church.
Unlike previous Assisi events, there will be no praying together in public but rather time for individual prayer and silent mediation during a joint pilgrimage to the tomb of St Francis. Representatives of the world’s religious traditions will then recommit themselves to praying and working for peace in the world...