The man who last spring called for a "national conversation" on the conflicting demands of security and openness in government architecture initiated that discussion yesterday with a warning.

"We begin to look as if we are afraid," said Sen. Daniel Patrick Moynihan (D-N.Y.), describing the increased visibility of security precautions in Washington and fortresslike U.S. embassies abroad. "And we ought not," he concluded. "We are not a terrified society and we will not let them [terrorists] win."

Moynihan's remarks opened a day-long conference on the issue attended by more than 500 independent architects, engineers and builders along with numerous federal officials. The conference took place in the new Ronald Reagan Building and International Trade Center, one of the more open federal buildings in the nation.

Threats are real and serious, conferees were told. Handguns, pipe bombs, package bombs, car bombs "and on up" are weapons to be concerned about at Washington's federal buildings, said Jim Rice of the National Capital Response Squad of the FBI's Domestic Terrorism Program. The "on up" worries include nuclear, chemical and biological weapons, he said.

The nation's 260 embassies and consulates worldwide are subject to "clear and present dangers," said David Carpenter, assistant secretary of state for diplomatic security. Carpenter reported that there have been more than 3,000 threats to U.S. diplomatic installations and more than 70 temporary closings since the August 1998 bombings of our embassies in Kenya and Tanzania.

How to respond to such dangers and yet maintain the openness and accessibility necessary to a democratic government are the twin challenges facing all involved in federal architecture projects, said Robert Peck, head of the Public Buildings Service of the General Services Administration, which co-sponsored the symposium with the Department of State and the American Institute of Architects.

But if finding a "reasonable balance" between security and openness is the primary challenge, as U.S. Supreme Court Justice Stephen Breyer said, it often depends on who defines what is reasonable. "The bureaucratic nature of the decision-making process," Breyer said, often results in the most cautious decisions possible.

One of the problems, observed Gavin de Becker, author of "The Gift of Fear," is that public reactions to terrorist incidents and other catastrophes is often "unwarranted fear" as opposed to "true fear."

"People are looking for someone to blame," he said, and this attitude forces decision-makers to take cover. De Becker and other speakers called for more information about terrorist threats and more even-handed assessment of risks.

Overreacting to a particular threat--notably car bombs--while ignoring others is another flaw picked out by several speakers. J. Carter Brown, longtime chairman of the federal Commission of Fine Arts, blasted President Clinton's decision to close the White House portion of Pennsylvania Avenue NW four years ago in the wake of the bombing of the Alfred P. Murrah building in Oklahoma City.

"To shove the citizens way out to the north edge of Lafayette Park to look at one of their most important public buildings" was a mistake, Brown said. He pointed out that "if you really want to blow the place up you can do it from other places" in the city.

One cure to the quick fix, said Breyer, is for the client, architect and all involved in the building process to spend a lot of time defining and adjudicating the competing interests and needs. As a federal judge in Boston, Breyer, Judge Douglas P. Woodlock and others did just that in planning the new federal courthouse there. The building, designed by Henry Cobb of Pei, Cobb, Freed & Partners, has been hailed an outstanding work of architecture--reasonably secure but not forbidding.

In the "close and difficult cases," Breyer said, "there is an overwhelming and overarching need for openness" in architecture, a sentiment echoed by other speakers.

CAPTION: The Treasury building was part of the nationwide security tightening in 1996.