Believe it or not, it was only 50 years ago when the phrase "In God We Trust" first appeared on paper currency in the United States.

The phrase, which has been the country's national motto since 1956, has been the center of an ongoing dispute about the separation of church and state. Indiana officially joined the debate with the recent lawsuit challenging the "In God We Trust" license plates.

Americans' difference of opinion has led to numerous challenges regarding the phrase's constitutionality. Courts have ruled on everything from the acceptability of using "under God" in the Pledge of Allegiance to posting the Ten Commandments in courthouses.

Porter Superior Court Judge Roger Bradford remembers when the phrase "under God" was inserted into the pledge.

"I was in fourth grade when they changed it," Bradford said. "I had learned the pledge without that phrase so then I had to learn it with it. I think there was a little bit of discussion about the change, but it was nothing compared to all the lawsuits and everything today."

Bradford said he doesn't think the Constitution prohibits a reference to God, Allah or any other supreme being.

"Because this country was founded by Christians -- some of whom were escaping religious prosecution -- the reference to God is part of the history of this country. I think they get a little picky when they want to remove all references to it. You can turn the argument around and say that to have no recognition of a supreme being would favor atheists."

Because the issue is so subjective, ruling on whether something violates the Constitution's establishment clause can be difficult.

Taking a move from Supreme Court Justice Potter Stewart's playbook, Porter Superior Court Judge William Alexa said simply, "I know it when I see it."

According to Ivan Bodensteiner, professor of law at Valparaiso University, the courts have adopted a variety of approaches to evaluating the issue.

One method is deciding whether a "reasonable observer" would view the incident as a governmental endorsement of religion. Another has to do with whether the incident was "coercive" in any way -- making an individual feel obligated or pressured. A third approach is to look at the purpose of the incident and the overall effect of it.

Bodensteiner said the prominence of today's legal challenges may be a result of a more conservative Supreme Court.

"Over the last 10 to 15 years, the Supreme Court has been more willing to tolerate government involvement with religion," Bodensteiner said. "They've sent a signal that 'We'll be less likely to find a violation of the establishment clause.' As a result, the signal opened the door for governments at all levels to be more bold with religion."

With the holiday season approaching, the debates will inevitably grow louder, as people challenge nativity scenes in courthouses, Christmas trees in government buildings and other representations of faith. As far as the overall trend of the dispute, however, Alexa sees no end.

"I think it'll keep going as long as the issue stirs the pot for people," Alexa said.