Ecumenical, evangelical and Roman Catholic leaders have conceded that there are still many obstacles to unity in the body of Christ but stress they remain committed to the journey.
Dr. Olav Fykse Tveit, general secretary of the World Council of Churches, Dr. Geoff Tunnicliffe, international director of the World Evangelical Alliance, and the Most Rev. Brian Farrell, secretary of the Pontifical Council for Promoting Christian Unity, were speaking to journalists on Saturday at Edinburgh 2010, a major conference taking place this week to mark 100 years since the World Missionary Conference was held in the Scottish capital in 1910.
Bishop Farrell was the least optimistic about efforts towards unity.
"Only in the in the recent past have we realized how deep our ethical differences are. Division is a very serious problem," he said. "We are on a journey together that instead of becoming more simple is becoming more complicated.
"We need to be even more committed to working out the path that leads to closer commitment and communion even if we do not have clear ideas about the future."
Although the Roman Catholic Church, evangelicals and ecumenicals have been in sustained dialogue over the last few decades, they remain at odds with each other over a number of issues, including the status of women, human sexuality, and what shape mission to the world should take.
When asked if it was possible for the three traditions to present a common faith to the world at this present time, Farrell answered, "No."
He added, however, that the Roman Catholic Church would continue to work together with other traditions and that it remained "totally committed to finding a way forward."
Tunnicliffe of the WEA said it was important to see conferences like Edinburgh 2010 within the broader context of ongoing collaboration between the different Christian traditions.
He pointed to a diverse meeting of Christian leaders in Geneva last week to discuss a joint document on proselytism and conversion. The group, made up of representatives of the mainline denominations and traditions, has been working on a common set of guidelines for the last three years.
Tunnicliffe said he hoped the spirit of that dialogue would influence the conference and future meetings among Christians.
"There's some very active work that is continuing to take place," he maintained. "We recognize that there are some significant differences within our community and around how we engage, but there is an ongoing commitment to finding ways to talk to each other. It's an ongoing work."
He added that the diverse nature of the body of Christ need not be a hindrance to unity but could rather demonstrate true unity to the world.
"To me the power of the unity of our witness is found in our diversity. It would be very easy if we were all the same to be one, but the fact that we are diverse, it's in our diversity that the world would see us coming together," he said.
"That's the power of oneness of the Gospel and that's what drives us as evangelicals – a commitment to respond to the prayer of Jesus ('that they may be one'), based on the authority of His word and its truth."
WCC's Tveit warned Christians not to give in to "self-fulfilling pessimism" regarding efforts towards unity but instead see what they could do together even where they were aware of divisive issues.
"We should not divide our calling but share our calling – we shouldn't say 'You do this and I do this,' 'You work for mission and we work for unity,' 'You work for justice and we work for evangelism.' There is no such division in the Gospel and there is no such division in Christ," he said.
He spoke positively of a common concern among all Christians for justice, peace, and creation care but admitted there were still many challenges facing the global body of Christ.
"At least there is now a deeper mutual recognition that we all want to share the Gospel," said Tveit. "It is the same Gospel we want to share and convey to the next generation. We don't have to accuse one another of not being interested in doing that.
"But I also recognize very strongly here that we have a common responsibility for this world. We cannot ignore the challenges of this world and we cannot ignore that we are not the only believers in this world.
"This conference at least makes it clear that Christianity is a global religion but it is still difficult to give a proper expression to that and that is still a challenge to all of us."