A woman in a red car pulls up to a tollbooth at the San Francisco-Oakland Bay Bridge. "I'm paying for myself and the six cars behind me." She says with a smile, handing over seven commuter tickets.

One after another, the next six cars arrive at the booth, money in hand. "Some lady up ahead already paid you fare," says the collector. "Have a nice day."

The lady, it turned out, had read a note taped to a friend's refrigerator : Practise random kindness and senseless acts of beauty. The words leaped out to her, and she wrote them down.

Judy Foreman spotted the same phrase on a warehouse wall 120 kilometres from her home in San Fransisco. When she couldn't get it out of her mind, she finally drove all the way back to copy it down. "I thought it was incredibly beautiful," she said, explaining why she writes it at the bottom of all her letters. "It's like a message from above."

Her husband, Frank, a teacher likes the saying so much he posted it on the wall for his seventh graders, one of whom was my daughter. A local columnist, I put it in the paper, admitting I liked it but didn't know its source or real meaning.

Two days later, I heard from Anne Herbert, 40, a house sitter in Marin County, California. She had jotted the phrase down on a restaurant place mat after mulling it over for days. "Here's the idea," she says, "if you think there should be more of something, do it - randomly. Kindness can build on itself as much as violence can."

Now the message is spreading, on bumper stickers, walls and business cards. And as it spreads, so does a vision of "guerrilla goodness."

A passerby may plunk a coin into a stranger's parking meter just in time. A group of people with pails and mops may descend on a run-down house and clean it from top to bottom while the elderly owners look on, amazed. A teenager shovelling snow may be hit by the impulse and shovel his neighbour's driveway too.

Senseless acts of beauty spread. A man plants daffodils along a roadway. A concerned citizen roams the streets collecting litter in a supermarket cart. A student scrubs graffiti from a park bench. It's a positive anarchy, a gentle disorder, a sweet disturbance.

They say you can't smile without cheering yourself up. Likewise, you can't commit a random act of kindness or beauty without feeling as if your own troubles have been lightened - because the world has become a slightly better place.

And you can't be a recipient without feeling a pleasant jolt. If you were one of those commuters whose bridge fare was paid, who knows what you might have been inspired to do for someone else? Wave someone on in the intersection? Smile at a tired clerk?