The US Capitol has 23,000 visitors a day. The huge majority of these, Americans and foreign visitors alike, support the democratic processes embodied by this building.
A tiny number come with violence in mind, deluded by conspiratorial fears or zealotry. The man who invaded the Capitol last Friday, killing two policemen and wounding a tourist, was one of them.
He was known to the Secret Service. But that agency each month investigates 200 individuals who have threatened the president and other leaders. It can't track them all.
So close off the Capitol to lessen the threat? No, as President Clinton, Speaker Gingrich, and many others have said, that would be the wrong response. The people need ready access, to feel part of democracy.
Security, however, has been tightening for decades. In earlier times, even during the extreme tensions of the Civil War, public buildings were wide open. Lincoln was often accosted by total strangers as he walked the White House halls.
That extreme of openness is long gone. But modern technology and careful training can meld access, a welcoming atmosphere, and security. The guards in the Capitol, such as the dedicated public servants who gave their lives Friday, are models of good-natured vigilance.
Their work is reinforced by every citizen who cherishes democracy's ideals and prays for their protection.