“Faith is part of the fabric of our country. It always has been and it always will be. As you, Your Holiness, have said, faith is not a problem for legislators to solve but rather a vital part of our national conversation. And we are proud of that.”

That was how Great Britain’s Prime Minister David Cameron thanked Pope Benedict XVI for his recent visit there, in which he spoke unapologetically against the culture of relativism and secularism. “You have really challenged the whole country to sit up and think,” said Cameron, “and that can only be a good thing.”

Cameron paid homage to that which once was a given in so much of Europe, speaking above a political noise that is not always open to truth. It’s advice we ought to heed here across the pond.

Fifty years ago Sept. 12, in a famous speech to the Greater Houston Ministerial Association, John F. Kennedy announced his belief “in an America where the separation of church and state is absolute.” He said he believed that a president’s religious views should be “his own private affair, neither imposed by him upon the nation, or imposed by the nation upon him as a condition to holding that office.”

Which is absolutely the wrong approach for the Catholic in public life. Kennedy’s principle, of course, has a rich history, with even Catholic politicians expressing such things on Catholic campuses; by now, being merely personally opposed to evil on the Notre Dame campus might be among the least outrageous of its fruits.

This is why, 50 years later, another Catholic politician, considered a long shot for president, former Pennsylvania Sen. Rick Santorum gave a response to Kennedy in a Houston speech, at the University of St. Thomas there.

Right from the start, Santorum pushed back against the Kennedy principle. At a time when so many Americans are looking with a renewed enthusiasm at the Constitution, Santorum paints the Kennedy principle as not of the founding: “The idea of strict or absolute separation of church and state is not and never was the American model. It was a model used in countries like France and until recently Turkey, but it found little support in America until it was introduced into the public discourse by Justice Hugo Black in the case of Everson v. The Board of Education in 1947.”

He acknowledged, too, that “while the phrase ‘separation of church and state’ doesn’t appear in the Constitution, the concept of keeping the government apart from religion does.” Contrary to longtime Santorum critics — the senator was a leader on a whole host of issues during his tenure in the Senate, but is especially known for his leadership on life-and-marriage issues — he’s not looking to establish a theocracy.

“Our founders’ vision,” Santorum continued, “unlike the French, was to give every belief and every believer and nonbeliever a place at the table in the public square. Madison referred to this ‘equal and complete liberty’ as the ‘true remedy.’

“Our country hadn’t always lived up to that ideal — in particular with respect to Jews and Catholics, thus the legitimate reason for Kennedy’s speech. But what JFK advocated sounded more like Ataturk than Madison — that religious ideas and actors were not welcome in public-policy debates.”

Kennedy wanted to alleviate Protestant and other concerns about his Catholicism. But he did something much more dramatically far-reaching. Kennedy, according to Santorum, “advanced a philosophy of strict separation that would create a purely secular public square cleansed of all religious wisdom and the voice of religious people of all faiths. He laid the foundation for attacks on religious freedom and freedom of speech by the secular left and its political arms like the ACLU and the People for the American Way. This has and will continue to create dissension and division in this country as people of faith increasingly feel like second-class citizens.”

Santorum’s wasn’t the first and won’t be the last speech to push back against Kennedy’s Houston speech. Mitt Romney’s Houston speech on “Faith in America” in 2007 was in part a reaction to Kennedy’s approach. Romney’s Mormonism was as controversial as Kennedy’s Catholicism had been, and “smart” politicos advised him to take a tack similar to Kennedy’s. Even before giving the speech, Romney demonstrated a very different and very healthy inclination, one much more in keeping with our founding. He declared: “I know there are some people hoping that I will simply declare in some way that my church is all well and good but that I don’t really believe it and I don’t try to follow it. That’s not going to happen. I’m proud of my faith. I love my faith. It is the faith of my fathers and mothers. I do my best to live by its teachings. And it in every way would teach me to follow the Constitution and follow the rule of law and recognize that my duty is to my country.” In the speech he ultimately gave, he said: “In recent years, the notion of the separation of church and state has been taken by some well beyond its original meaning. They seek to remove from the public domain any acknowledgment of God. Religion is seen as merely a private affair with no place in public life. It is as if they are intent on establishing a new religion in America — the religion of secularism. They are wrong.”

Archbishop Charles Chaput of Denver, a good shepherd of clarity, also gave a Houston speech on faith and civic life. Last March, at Houston Baptist University, he announced: “I’m here as a Catholic Christian and an American citizen — in that order. Both of these identities are important. They don’t need to conflict. They are not, however, the same thing. And they do not have the same weight. I love my country. I revere the genius of its founding documents and its public institutions. But no nation, not even the one I love, has a right to my allegiance, or my silence, in matters that belong to God or that undermine the dignity of the human persons he created.”

Pope Benedict raised some similar concerns during his speech at Westminster Hall this September, as David Cameron alluded to. He said: “I cannot but voice my concern at the increasing marginalization of religion, particularly of Christianity, that is taking place in some quarters, even in nations which place a great emphasis on tolerance. There are those who would advocate that the voice of religion be silenced, or at least relegated to the purely private sphere. There are those who argue that the public celebration of festivals such as Christmas should be discouraged, in the questionable belief that it might somehow offend those of other religions or none. And there are those who argue — paradoxically with the intention of eliminating discrimination — that Christians in public roles should be required at times to act against their conscience. These are worrying signs of a failure to appreciate not only the rights of believers to freedom of conscience and freedom of religion, but also the legitimate role of religion in the public square. I would invite all of you, therefore, within your respective spheres of influence, to seek ways of promoting and encouraging dialogue between faith and reason at every level of national life. … I would suggest that the world of reason and the world of faith — the world of secular rationality and the world of religious belief — need one another and should not be afraid to enter into a profound and ongoing dialogue, for the good of our civilization.”

This is a challenge for every man and woman who ventures into politics or has anything to do with politics — which is to say, all of us citizens. As Archbishop Chaput put it: “A Christian life begins in a relationship with Jesus Christ; and it bears fruit in the justice, mercy and love we show to others because of that relationship.” If your life begins that way, your political life will necessarily flow from it. The truly Christian voter or public servant cannot divorce or subdue or compartmentalize faith and have integrity. We should be grateful to everyone who provides clarity, throwing moral sense over the so-called wall that separates us in the public sphere from the meaning of our lives. Rick Santorum — who as a U.S. senator heightened our sense of responsibility in the lives of the poor who were victimized and dehumanized by the Great Society welfare system, who defended the lives of the most vulnerable among us, who defended marriage long before it was a winning electoral issue — doesn’t have to become president to have made a contribution in making clear how powerful an element of American lives the freedom to be religious in the United States of America is.

As Santorum put it in his Kennedy corrective, we have “the opportunity [to] not only preserve but build on the founder’s vision of freedom supported by virtue, which in turn is supported by a vibrant faith — a mutually strengthening interface of church and state.” We should be confident in truly living our faith, prudently and authentically — not simply as rhetoric where it’s safe or politically advantageous. We do not truly know and love God if we do not let ourselves be his instruments — at home, at work, at the voting booth, on the floor of Congress. We’re free to do that. And we’re made to do that.

Kathryn Jean Lopez is editor-at-large of National Review Online and a nationally syndicated columnist.