Kevin J. "Seamus" Hasson, founder of The Becket Fund for Religious Liberty, poses for a photo on May 14 in Herndon. (Ricky Carioti/The Washington Post)

Lawyers and advocates who work on the hot-button issue of religious freedom are a passionate lot; they speak about their cause in nearly life-and-death terms. Even so, religious freedom can make for dry dinner-party conversation. And religious-freedom advocates don’t smile much when they’re on TV.

Which is why Seamus Hasson has always stood out.

Since founding the District-based Becket Fund for Religious Liberty law firm 20 years ago, the vivacious theologian-attorney became known for conducting business over long, boozy, gourmet lunches and bear hunting, all with his hallmark wry sense of humor (he once sent his mother-in-law a cactus to commemorate their prickly relationship).

“The great thing about Seamus, unlike some in those circles, he was great fun. Dead serious about his mission, but he is no Puritan — not by a long shot,” said Tom Carter, a former Becket Fund spokesman. “Could have been the Irish single malt, but several times he had me laughing so hard I was in tears.”

Hasson’s vision and will has led Becket from a one-man show in 1994 to the Supreme Court, where justices on Monday ruled in Becket’s favor, agreeing that closely held corporations can have religious objections. When the case was argued this spring, some said it could affect church-state relations for decades. Becket’s client, Hobby Lobby, a mega-chain of craft stores, challenged the White House and the Affordable Care Act, which requires employers to cover all kinds of birth control, even forms to which owners have a religious objection.

Seamus Hasson is seen with Pope John Paul II in Rome in 1995. Kevin J. “Seamus” Hasson is the founder of the Becket Fund and served as its first President from 1993 until his retirement in 2011. (Becket Fund for Religious Liberty)

Among the cluster of law firms that seek to push back on limitations on religion in the public square, Becket is considered perhaps the most prestigious, with a roster of lawyers who clerked at the Supreme Court. Once tiny, it now has 30 staff lawyers and a $5 million budget. And though it started with mostly conservative Catholic staff and supporters, Becket — unlike some similar firms — sometimes represents non-Christians as well, including Muslim police officers kept from growing their beards and Santería priests who wanted to ritually slaughter animals including chickens and goats for worship in their homes. In 2012 Becket lawyers successfully defended at the Supreme Court the right of religious organizations to hire — and fire — leaders in a ruling that some called the most important on religious freedom in decades.

Yet as Becket and religious liberty are having a major moment in the spotlight, Hasson is absent. With Parkinson’s disease forcefully advancing, he retired in 2012 and this week was engaged in his regular routine: Morning Mass with his wife near his home in Herndon, and then some reading time at Starbucks.

But Hasson has found another way to keep speaking. Even as the arc of his days is dictated by medication and exhaustion, the 57-year-old father of seven, ages 13 to 29, is writing a book he hopes will take some of the culture-war edge off what has become one of the most polarizing issues of the day. In an argument sure to rile some on both sides, Hasson’s book posits that religious liberty can be seen as a philosophical issue, not a religious one.

Saying that rights come from human beings is dangerous, because people can then decide — as they did during horrors like the Holocaust, for example — to take them away, Hasson said during a recent talk at an Italian restaurant near home, the only interview he has given since retiring. “But the question ‘Is there a God?’ doesn’t have to be a religious one. The government can’t take religious positions but it can take philosophical ones.”

Hasson hopes this argument could resolve high-profile government speech cases including those about the Pledge of Allegiance, for example.

Hasson’s fans say the affable bon vivant — who wrote a book in 2005 subtitled “Ending the Culture War Over Religion in America” — left a noticeable hole in the small religious-freedom profession when he retired.

“With his personal charisma and charm and big heart, he was the person who would have been able to bring a lot of people to an area of compromise on religious liberty,” said William Mumma, a former Wall Street executive who has been Becket’s president since Hasson retired. “Right now we could use that so much. Things are so polarizing.”

But others say Hasson, who worked in the Reagan Justice Department for then-Assistant Attorney General (and now Supreme Court Justice) Samuel A. Alito Jr., and Becket are deeply part of the problem, over-hyping the threat to diverse religious practice and feeding partisan divide.

It’s common for opponents of the White House contraception mandate — including many of Becket’s clients and supporters — to accuse President Obama of launching a “war on religion,” one aimed in particular at the Catholic Church.

Becket’s essential argument, says the Rev. Barry Lynn, a church-state separation advocate, is that more exemptions and funding for religious groups and unrestrained public prayer are positive for the United States and for religion.

“What the Becket Fund doesn’t acknowledge is that in America 2014, the tremendous overwhelming benefit of all that goes to the majority religion,” meaning Christianity, Lynn said. “You have to look at the reality of today.”

Last month, when the Supreme Court affirmed the right of legislative bodies to open meetings with sectarian prayer, advocacy groups representing religious minorities were nearly unanimous in their opposition. Becket celebrated the decision.

The spiritual side

Growing up, Hasson was the one student at his Rochester Catholic school who wanted to hit the revival of evangelist Billy Graham.

”He was always interested in the spiritual side of things,” said Gen. Jim Lariviere, a Marine who grew up with Hasson. “Even my mom would talk about it, how he’s different from the other kids.”

Voted most likely to succeed in high school, he then pursued a degree in theology at Notre Dame before heading to law school, where on the first day he entertained classmates with his pipe dream: to start a law firm to defend religious liberty.

Then, as now, he saw himself as a bridge between Americans who view religion as smoke and mirrors and those who see this country as a Christian nation. He says he thought that Vatican II, a major meeting of the Catholic Church in the 1960s that for the first time codified respect for different paths to God, had the answers.

After a few stops in corporate law and then the Justice Department, Hasson founded Becket. He thought its work could protect individual conscience rights and check the power of government by promoting free exercise of religion. He doesn’t understand why religious minorities always seem to be on the other side.

“I’ve asked myself that dozens of times,” he said.

He is proud that Becket’s public arguments about the conflict between same-sex marriage and religious freedom don’t pass judgment about gay relationships or what’s best for children. He says he misses the climate when Becket began, when he’d bet a pizza on cases with ACLU lawyers on the other side.

“We could yuk it up before and after debates. There was a sense you could be a happy warrior. That doesn’t seem to be there as much anymore,” he said.

But Hasson also knows that in Becket’s early years, some at the firm were hesitant about hiring religious minorities. The board and donors until recently were overwhelmingly Catholic.

“We had to overcome this,” he says now.

And they did. Staffers now include a Mormon, a Muslim and Southern Baptist leader Russell Moore serves on the board, as well as other non-Catholics.

Hot-button issues

The Becket Fund stands out for its top-notch lawyers and willingness to support clients of any faith, said Doug Laycock, a University of Virginia law professor who has worked with and against the firm.

But Laycock worries that, in an increasingly diverse and complex country, conservative Christian groups have made “religious freedom” shorthand for opposition to gay marriage and abortion, or contraception in the case of Hobby Lobby.

Conservative churches, he says, are “standing in the way” of steps toward sexual equality such as gay rights and an absolute right to contraception, “and making a lot of enemies for themselves and for religious liberty,” Laycock said.

To some degree, the hot-button issues have been good business for all sides.

“That’s how you raise money. People don’t bring out their checkbook when you say, ‘We have a reasonable disagreement with other Americans,’ ” Laycock said.

To hear advocates on all sides of the topic speak, it can seem like times are dire, that Americans’ religious freedom all hinges on a Supreme Court decision or an election. But Hasson these days sounds more ephemeral. Humans, in his view, seem destined to endlessly struggle with how they treat questions of transcendence. And now is his window to weigh in.

“One side says, ‘We’re cold organisms that drift aimlessly.’ [The other says,] ‘We’re noble creatures with our eyes focused to the horizon,’ ” he says at the restaurant, his body shaking as he speaks, but his face, his voice, the same as always — more pastor and professor than litigator.

Whatever happens at the Supreme Court, he is focused on his book and his children, and his hopes that they have understood their father’s philosophy. Happily, he thinks they are in the latter camp — noble creatures, idealists.

“Let’s put it this way,” he says proudly. “When we play Hearts, at least half try to shoot the moon.”