Ten years ago this week, William Thomas, a practitioner of the First Amendment as well as a believer in it, took up residence on the sidewalk across from 1600 Pennsylvania Ave. Since then, he and others have formed an above-ground underground, a small collection of antiwar demonstrators who have been the closest neighbors to the country's last two pro-war presidents. They turned Lafayette Park into Peace Park.

On this weekend as Washington's widest streets are commandeered by the Pentagon and military contractors to parade their hirelings and machines that did the slaughtering of at least 100,000 people in Iraq, Thomas will counter the mindless celebration of death with a vigil for life.

In front of the White House, he passes out pacifist literature, holds up antiwar signs and keeps on being, in a decade of iron tenacity, the defiant citizen that Amos, Isaiah, St. Francis, Tom Paine, Eugene Debs, Emma Goldman and other incorrigibles would link arms with were they to return.

Like all of those connoisseurs of dissent, Thomas has paid heavily for his disaffections with warlords and their authority. He has endured more than 40 arrests, with about a dozen convictions for civil disobedience. His jail time has been mostly weekends, except for a 90-day stretch for unauthorized camping. The National Park Service has been dogged in its efforts to block Thomas from being a happy camper. Regulations sprout from NPS like springtime tulips in the White House flowerbed.

The doubting Thomas is a short and sturdily built man who was in the jewelry business until 1975 when he took to heart a biblical passage about placing total trust in God. With few such absolutists on the planet, an Episcopal priest, the Rev. J. Ellen Nunally, who is also an English professor at George Mason University, has devoted the past year to interviewing Thomas and his peace vigilers. In time, she will write a book, one that goes beyond the first impressions that this is a sidewalk commune of nomads to reveal the group to be motivated by authentic religious ideals and democratic instincts. Others have found this to be true, including a teacher from a public high school three blocks away who invites Thomas to come discuss civics with students.

As America's most visible antiwar group, and having the choicest real estate outside of the Rose Garden, Thomas and his weatherbeaten friends are as accustomed to federal harassment as they are to being dismissed by the media as semi-loonies who, quaintly, prove that the First Amendment works: Tolerating a few sidewalk eccentrics verifies the superiority of the American system. The self-congratulation also allows the champions of the system to look away when prophets like Thomas show up with a suggestion or two on how governments could be truly humane if peacemaking were done in earnest.

The current suggestion from Peace Park is Proposition One, a proposed constitutional amendment that would require nuclear disarmament and create programs for converting weapons industries into peacetime industries. A Proposition One Committee has been formed to help organize state peace groups to get on voter initiative ballots.

The idea is visionary, revolutionary and unwieldy, and has everything going against it except for one plus: The goal of Proposition One is what George Bush and Mikhail Gorbachev have been proclaiming since each took office. By putting the idea of disarmament to a vote, the Peace Park initiative is acting on the thought of Dwight Eisenhower: "I like to believe that people in the long run are going to do more to promote peace than are governments. Indeed, I think that people want peace so much that one of these days governments had better get out of their way and let them have it."

When that happens, William Thomas will pack up and give over his space in Peace Park to the squirrels, who had it first. He'll donate his sign, "Trust God and Disarm Everywhere," to the Smithsonian and vanish. "I don't favor national boundaries, armies or governments -- not because they're evil but because they aren't necessary," he said the other morning on a bench near his sentry as Park Service mowers cut the lawn. "All that's necessary is a wholehearted belief in a God of love and life. The test of that wholeheartedness is the action it produces toward creating a peaceful world."

As a major tourist attraction in Washington -- free of charge, round the clock, accessible and memorable -- Peace Park and its keepers are a reminder this weekend that George Bush doesn't understand what's directly in front of his nose. On March 1, he said: "There is no antiwar movement."