He has three keys dangling from one end of his key chain. The top one, he explains, goes into the extra safety lock. The round one turns off the burglar alarm. The bottom one opens the door. When he was a kid, he tells me, the back door of the house was always unlocked. His own kids are taught never, never, to open the door to strangers.

She is seated next to me on the airplane. She looks over and says I should put my gold chain in my pocketbook when I get to New York. Haven't I heard about the kids ripping necklaces off women? I take it off.

She is traveling on business again. At the registration desk the clerk tells her that they have a new escort service. Someone is available to accompany her every time she goes to her room. Once she would have refused, now she accepts.

They are not paranoid, these people. Nor am I. We do not cower in distant suburbs afraid to come to the city for dinner. In fact, we all live in cities, and have evolved over time a certain pride in urban survival.

And yet something has changed.

Maybe it was the 13-year-old son held up on the way home from school by 17-year-old boys. Maybe it was the fourth time the car window was broken and the third time the stereo was stolen. Maybe it was the purposeful murder of John Lennon or the random murder of Dr. Michael Halberstam.

Or maybe there are simply too many incidents too close to home to brush off anymore.

But our resilience has been worn down, and so we shake our heads when we read Chief Justice Warren Burger's words to the American Bar Association: "What people want is that crime and criminals be brought under control so that we can be safe on the streets and in our homes and for our children to be safe in schools and at play. Today that safety is very, very fragile."

If Burger was out of place delivering an 11-point program as if he were an attorney general, he nevertheless clarified something that we already know: the urban spirit is turning into a fortress mentality.

We've all heard it in a dozen small, anxious ways. In the dinner-party gossip about crime that now matches, story for story, the gossip about love affairs. Which family on the street has broken up? Which family broken into?

The same people who talked incessantly about making a profit from their real estate now talk incessantly about protecting their real estate. Today they improve their homes with iron bars instead of bushes. They add locks instead of shutters.

There is an edge to life, sane and sad, of self-protection. The man who put on his necklace as a sign of free expression in the '70s takes it off for safety in the '80s. The woman who bought silver in the '50s as a tribute to financial security hides it in the '80s as a tribute to insecurity.

I don't mean to suggest that we are obsessed, that we quake in fear. We don't. But our guard is up more often in more places.

On the street, we may fantasize a plan of self-defense. In the elevator, in the ladies' room, in the subway, an image of danger may flit across our consciousness for just a moment. We may begin almost superstitiously to avoid some place that seems dangerous to us, whether it's a red light district or an underground garage.

I have not even mentioned gun permits and California self-protection courses in the use of tear gas.

"Are we not hostages within the borders of ourselves because of alarms and locks?" asked Burger.

Yes.

It isn't just the criminal offensive that affects our lives; it is also our own growing defensive. When we learn to turn on the alarm, put the jewelry in the refrigerator, push down the buttons in the car, think twice about walking down a street, our lives are diminished.

The man looks at the burglar alarm keys in his hand. He hates them. I tuck the chain inside my pocketbook and resent it. The woman is escorted to her room and feels smaller. All of us are somehow less free.