All trips, however disheveled, acquire themes. The purpose of this one was a family rendezvous at a distinguished hospital in Washington, D.C. to have a 7-year-old grandson’s rare ailment diagnosed. It played out against the background of sniper terror.

The first impression of the city was civility, from cab drivers, sales clerks, waiters, vendors of espresso. Post-9-11 New York had been the same. Danger and disaster seem to strengthen the communal bonds.

D.C. differs from other cities in its political edge, of course. A poster in the subway showed three pigs being launched into outer space, propelled by rear-end jets. The missile defense initiative was “Enron in Space,” it said, a $238 billion “pig out” of greed and deceit.

Another poster attacked George Bush for degrading the environment. No tin pot dictator would have to suffer such public reproach. But the president of the United States couldn’t send a goon squad around to tear down the poster and punish his critics. Three cheers for freedom of speech.

“Please don’t feed wild animals,” said a sign on the National Mall. A puritanical lecture on the dangers of violating nature’s food chain followed. It had to be the work of some functionary in the Federal Bureau of Squirrel Protection, since the only wild animals in sight were squirrels. Their remarkable tameness suggested that the sign had been ignored. Only in Washington, D.C.

We ventured between poles of violence and beauty, affection and fear. One night we watched a television documentary that reviewed Frank Lloyd Wright’s masterpieces and paid tribute to his unshakable vision. The next night, it was Bruce Lee kicking and screaming his way to the top of a pagoda where ultimate evil awaited him in the shape of Kareem Abdul Jabbar. A redeeming spiritual message was promised, but we waited for it in vain.

An exhibit of the works of Pierre Bonnard offered us a celebration of life and light. Sunshine poured through windows transmuting humble objects fruits, flowers and baskets of bread into molten gold. It was all about blooming, openness, the magic of colors and the miracle of seeing. Bonnard paid homage to “the validity of the first impression.” He could paint a tree trunk purple and make it seem real.

Back on the street we hurried along and kept an eye out for white vans until we realized that white vans are ubiquitous. In newspapers we saw photos of people crouching to fill their cars with gas and read persuasive speculations identifying the sniper as a member of al-Qaida or a demented fan of violent video games.

A cartoon my grandson watched dramatized a cosmic showdown between a pair of virtuous brothers and an evil genius obsessed with ruling the universe. The cartoon clichas a parody of current reality: a murderer who imagines he is God, rulers of nations intoxicated with dreams of power, rattling not sabers but doomsday bombs.

On a beautiful day in the nation’s capital, we wondered why anyone would be interested in ruling the universe. Few other tourists were out; school field trips had been canceled because the streets were deemed unsafe, so we had Lincoln’s memorial almost to ourselves.

The astonishing words of his second inaugural address seemed appropriate: “Yet, if God wills that it (the Civil War) continue, until all the wealth piled by the bond-man’s two hundred and fifty years of unrequited toil shall be sunk, and until every drop of blood drawn with the lash, shall be paid by another drawn with the sword” It was a reminder of our nation’s original sins. There was no escape from violent themes that day.

Our grandson made the most of his plight. Surrounded by medical specialists, he demanded 25 cents for answering each question they posed to him. He cajoled me into piloting a flight simulator in the Smithsonian, which I sent into a nightmare series of nauseating, topsy-turvy spins, to the amusement of a crowd of spectators.

Outside, the world seemed safe, sane, serene. Street sweeping machines, buses, delivery trucks went about their errands. Pedestrians waited for traffic lights to change. Strangers observed the common courtesies: “Pardon me,” “After you,” “Have a nice day.” Civilization is a work of art, an intricate web that can be torn by a single man with a gun or bomb.

What does it all mean? Why are there some who despise beauty, order, family, health, pleasure, to whom love of life is a weakness?

At Dupont Circle, an affluent area of elegant townhouses and tree-lined lanes, the homeless sat on benches wrapped in gray blankets. Two men played chess; another threw his head back and sang ecstatically to the music on his earphones, while another gazed into a miniature mirror with a gilded ornate frame teasing his hair. Life in its infinite, precious manifestations goes on.

In a small gallery with no more than a dozen other visitors, we saw a Japanese screen depicting the journey of a powerful shogun. As he and his retinue crossed over a bridge, his servant accidentally dropped his master’s fan into the rushing stream. It could have been an occasion for anger and rebuke, but the travelers saw things differently that distant day.

“Struck by the sudden, poignant reminder of beauty’s fragility and fleeting nature, the shogun’s retinue followed suit, casting their fans into the stream.”

The tableau was timeless. The moment had been arrested in lacquered shades of silver and gold. The master didn’t shout or beat the servant for his ineptness. The stream was still, the white rapids arrested, a leaf storm of fans encrusted with gems frozen in mid-air.