On this date 128 years ago, the U.S. Supreme Court took a major step toward defining the separation of church and state. Reynolds v. United States, decided on Jan. 4, 1879, was one of the first cases to consider what the First Amendment means by "Congress shall make no law respecting an establishment of religion or prohibiting the free exercise thereof...."

George Reynolds was a practicing Mormon living in the Utah Territory. Like many of his fellow Utahns, he adhered to the religious dictate that he take more than one wife. Refusal to practice polygamy, he believed, would result in eternal damnation. The federal government, however, took a different view. Congress passed a law criminalizing bigamy, and Reynolds was arrested, charged and found guilty.

Reynolds appealed to the high court, leaving the justices to decide whether religious belief and practice could override a law regulating conduct. Writing for a six-justice majority, Chief Justice Morrison R. Waite ruled that Reynolds' religious opinion did not excuse him from following the bigamy law.

Waite reasoned that the anti-bigamy law did not prohibit the free exercise of religion, but rather was a legitimate ban on a dangerous practice. Waite wrote at length about the Amendment's genesis, highlighting the persecution the Founders wanted to avoid with the First Amendment. Waite's narrow view of the First Amendment Free Exercise Clause limited the prohibition to belief only; the government could step in once the belief manifested itself in practice.

Today, of course, mainstream Mormons no longer practice polygamy. Church leaders repudiated plural marriage decades ago. But church-state separation advocates see the Reynolds decision as a milestone for reasons that go beyond the facts of the case. Reynolds was the first time the Supreme Court cited Thomas Jefferson's "wall of separation" metaphor to describe the proper relationship between religion and government.

After his election as president of the United States, Jefferson wrote to a group of Danbury, Conn., Baptists to thank them for their support and to express his views on religious liberty. In his Jan. 1, 1802 missive, he said that the American people through the First Amendment had built "a wall of separation between Church and State."

Chief Justice Waite stressed the metaphor's authority in his opinion: "Coming as this does from an acknowledged leader of the advocates of [religious liberty,] it may be accepted almost as an authoritative declaration of the scope and effect of the amendment thus secured."

Since first appearing 128 years ago in Reynolds, Jefferson's "wall of separation" metaphor has become synonymous in the public mind with the Constitution's requirements. Many Supreme Court opinions have also reaffirmed Jefferson's idea, although the high court has been less devoted to that protective barrier than many of us would like.

In a recent case involving taxpayer aid to parochial schools, Justice John Paul Stevens wrote, "Whenever we remove a brick from the wall that was designed to separate religion and government, we increase the risk of religious strife and weaken the foundation of our democracy."

The "wall of separation" between church and state is more than one man's opinion. The "wall" symbolizes a very real constitutional principle. As Supreme Court Justice Hugo Black explained in one landmark church-state case, "The constitutional prohibition against laws respecting an establishment of religion must at least mean that in this country it is no part of the business of government to" meddle in religion.

This is the "separation of church and state," and our religious freedom depends on it.