The scale of the challenge and the glimmer of new possibilities in interreligious understnading is on display at the 16-18 July international interfaith conference convened in Madrid by the Muslim World League.
The meeting follows an initiative by Saudi Arabia's King Abdullah in bringing Muslims together.
One of the participants is ex-British Prime Minister Tony Blair, a hate figure for many Muslims because of his key role in the Iraq war.
Mr Blair, who has made interfaith work one of his priorities since leaving office, told reporters today that without co-existence among the religions, world peace would be very difficult to sustain.
His message echoes that of leading Catholic theologian Hans Kung, whose Global Ethics Foundation seeks to bring together people of goodwill from different backgrounds and beliefs.
The World Council of Churches is being represented at the event by one of its presidents, Patriarch Abune Paulos, head of the Ethiopian Orthodox Tewahedo Church, and by Metropolitan Emmanuel (Adamakis) of France, from the Ecumenical Patriarchate of Constantinople.
Also attending is Lebanese Minister of Culture Dr Tarek Mitri, a former WCC staff and a member of the Greek Orthodox Patriarchate of Antioch and all the East, and the WCC's Director of Inter-religious dialogue and cooperation, the Rev Dr Shanta Premawardhana.
Organized by the Muslim World League at the initiative of Saudi Arabia's King Abdullah bin Abdul Aziz, the three-day long "International Conference for Dialogue" is gathering some 200 participants representing Islam, Christianity, Judaism and Buddhism.
Islam is the official state religion of Saudi Arabia, while non-Muslim religious services and symbols are banned within the kingdom's territory.
This has led to accusations of appeasement and hypocrisy by civil rights groups.
Tony Blair said this morning that there was a "glimmer" of change sigballed by King Abdullah's role at the event, however, and that the meeting was part of a long and difficult process of encouraging global religious freedom and dialogue.
He spoke of the possibility of a Catholic Church being allowed in the Saudi kingdom. For Protestants and other religious groups, prospects of recognition are thin, however.