The American kickoff of the Tony Blair Faith Foundation last week unintentionally illustrated the mountain of misunderstanding the former British prime minister has undertaken to scale. At an event designed to further mutual religious sympathy, two of the panelists — including the president of Yale University, Richard Levin — casually asserted that religious Americans who support pro-life restrictions on international family planning assistance are as doctrinaire and exclusionary as Saudi extremists. Pro-life Catholics and evangelicals? Wahhabi extremists? What’s the difference?

Clearly, mutual religious sympathy has a ways to go in places such as Yale.

Speaking to me after the event, Mr. Blair was patient, arguing that “could not be what they intended.” He admitted that on issues such as the rights of women, things “will be difficult,” but insisted that “there is a larger unity.” He has no intention of being distracted from his mission.

That mission, as usual, takes the form of a sophisticated intellectual argument and a third-way rejection of ideological extremes. As the only European politician who still seems to take September 11, 2001, seriously, Mr. Blair is highly critical of “extremist and exclusionary” religion. He draws a stark global dividing line, not between left and right or north and south, but between pluralists and totalitarians. His new foundation intends to support people who oppose extremism, especially among the young.

But Mr. Blair is also critical of an “aggressive secularization,” which, he told me, makes it easier to “forget a higher calling than the fulfillment of our own desires.” Religious faith, at its best, not only encourages idealism, it provides an explanation and foundation for human rights and dignity, “an inalienable principle, rising above relativism and expediency.” This does not “eliminate the painful compromises of political existence,” Mr. Blair recognizes. But it does mean that “not everything can be considered in a utilitarian way.” Mr. Blair defends a pluralism without relativism, a tolerance consistent with a belief in religious and moral truth — indeed, a tolerance that arises from within those convictions.

It could not have been easy for Mr. Blair to embrace this calling as “the rest of my life’s work.” In British politics, religious conviction is tolerated as a private vice — like the collection of rare Victorian pornography. It may be understandable, but why would one talk about it in public?

Some of Mr. Blair’s motivation is clearly personal. He is a recent Catholic convert. (There are, by the way, now more Catholic than Anglican churchgoers in Britain for the first time since the Reformation.) During a speech at Westminster Cathedral in early April, Mr. Blair talked movingly of God as “selfless love, merciful, and an infinite dispenser of grace.”

But his main argument is public and visionary. Religion, Mr. Blair argues, is not going away, as secularists have expected and predicated for centuries. For millions, he noted in his Westminster speech, it is “the motive for their behavior, the thing which gives sense to their lives and purpose to their journeys — which makes life more than just a sparrow’s flight through a lighted hall from one darkness to another, in that memorable image of the Venerable Bede.” While religion may sometimes be a source of conflict, it has often been a source of reform and idealism — as in the fight against slavery, apartheid, and genocide. The goal of his faith foundation, he explained to me, is for the major faiths “to work together against injustice rather than prey — that’s p-r-e-y — on injustice.”

And the first injustice Mr. Blair’s foundation has chosen to confront is malaria, in cooperation with a splendid organization called Malaria No More. Mr. Blair’s vision of ecumenism is not focused on endless dialogue but on collective action. Malaria is an enormous moral challenge, taking more than a million lives a year, mainly of children under five. The band across central Africa where malaria is endemic is also a region where Muslim-Christian tension often runs high. About 40% of malaria victims in sub-Saharan Africa are Muslim. So fighting malaria is the issue most likely to bring Muslims and Christians together across their durable divisions. And, Mr. Blair adds practically, churches and mosques are essential “distribution centers” for the bed nets that save young lives.

“Faith,” Mr. Blair argues, “is not an historical relic but a guide for humanity on its path to the future. A faithless world is not one in which we want ourselves and our children to live.”

It is a new and unpredicted role for Tony Blair: the faithful servant against a faithless world.