Johanna Workman
Marc Day kneels and prays during a memorial ceremony on the National Day of Prayer and Rememberance in the Cathedral of the Madeleine, Friday, September 14, 2001. Photo/Johanna Workman

President Barack Obama has declared Thursday a National Day of Prayer, inviting "all citizens of our Nation, as their own faith directs them, to join me in giving thanks for the many blessings we enjoy," and calling upon "individuals of all faiths to pray for guidance, grace, and protection for our great Nation as we address the challenges of our time."

This year's National Day of Prayer does not come without some multi-faceted controversy, but U.S. presidents since George Washington have called for national "fasting, humiliation and prayer" to "acknowledge the gracious interpositions of Providence" and "unitedly implore the Protection of Heaven." In 1952, President Harry S. Truman signed a bill directing future presidents to determine a Day of Prayer each year on a date of their choosing. In 1982, an effort was launched to set a fixed date for the annual event, and in 1988 the law was changed to establish the date as the first Thursday in May.

In issuing the Day of Prayer proclamation, President Obama noted that "prayer has always been a part of the American story."

"On this National Day of Prayer," the 2012 proclamation continued, "we give thanks for our democracy that respects the beliefs and protects the religious freedom of all people to pray, worship, or abstain according to the dictates of their conscience.

"Let us pray for all the citizens of our great Nation, particularly those who are sick, mourning, or without hope, and ask God for the sustenance to meet the challenges we face as a Nation. May we embrace the responsibility we have to each other, and rely on the better angels of our nature in service to one another. Let us be humble in our convictions, and courageous in our virtue. Let us pray for those who are suffering around the world, and let us be open to opportunities to ease that suffering."

There is debate whether the national observance violates the establishment clause of the First Amendment to the U.S. Constitution. John Inazu, a law professor at Washington University in St. Louis, said this year's National Day of Prayer may be especially contentious because it falls on the 50th anniversary of the U.S. Supreme Court's famous Engel vs. Vitale decision, which ended prayer in public schools.

"Some religious believers will likely use the day of prayer to call attention to what they view as a regrettable and consequential decision," Inazu said.

As far as the "establishment clause" arguments are concerned, however, Inazu believes the current Supreme Court would reject any challenges to the National Day of Prayer observance because they would view it as "an inconsequential instance of ceremonial deism that shows equal regard to many religious beliefs."

Which may not sit well with either side.

"For many religious believers, prayer matters because its object – God – matters," he said, indicating that the notion of "ceremonial deism risks harming believers as well as non-believers."

The American Humanist Association and the Secular Coalition of America are sponsoring a National Day of Reason – which, not coincidentally, is also held on the first Thursday in May each year.

"The National Day of Prayer demeans millions of Americans who believe that reason, not prayer, is the way to solve the country's problems," said Maggie Ardiente, director of communications for the American Humanist Association.

The National Day of Prayer website counters that the day "is not sponsored or owned by any one group. Every American can observe the National Day of Prayer in his or her own way."

The National Day of Prayer Task Force called prayer "a vital part of our heritage," noting that the first national call to prayer occurred in 1775, when the Continental Congress asked the colonies to pray for wisdom in forming the new country, and the tradition has continued through 137 requests for nationwide prayers by various presidents of the United States.

"The National Day of Prayer has great significance for us as a nation," the task force's website says. "It enables us to recall and to teach the way in which our founding fathers sought the wisdom of God when faced with critical decisions. It stands as a call to us to humbly come before God, seeking His guidance for our leaders and His grace upon us as a people.

The task forces maintains that the day is one that "transcends differences, bringing together citizens from all backgrounds."