It's an underground slogan that's spreading across the nation.

It's a hot summer day in Sydney. A woman in a red Honda, Christmas presents piled high in the back, drives up to the Sydney Harbour Bridge toll booth. 'I'm paying for myselve, and for the six cars behind me,' she says with a smile.

One after another, the next six drivers arrive at the toll booth, dollars in hand, only to be told, 'Some lady up ahead already paid your fare. Have a nice day.'

The woman in the Honda, it turned out, had read something on an index card taped to a friend's refrigerator: 'Practice random kindness and senseless acts of beauty'. The phrase seemed to leap out at her, and she copied it down.

Judy Lamb spotted the same phrase spray-painted on a warehouse wall a hundred miles from her home. When it stayed on her mind for days, she gave up and drove all the way back to copy it down. 'I thought it was incredibly beautiful,' she said, explaining why she's taken to writing t at the bottom of all her letters, 'like a message from above'.

Her husband, Nathan, liked the phrase so much that he put it up on the classroom wall for his seventh-graders, one of whom was the daughter of a local columnist. The columnist put it in the paper, admitting that though she liked it, she didn’t know where it came from or what it really meant.

Two days later, she heard from Annabel Wood. Tall, blonde and forty, Annabel lives in Chatswood, where she house-sits, takes odd jobs, gets by. It was in a Chinese restaurant that Annabel jotted the phrase down on a paper placemat, after turning it around in her mind for days.

'That's wonderful!' a man sitting nearby said, and copied it down carefully on his own placemat.

'Here's the idea,' Annabel says. 'Anything you think there should be more of, do it randomly.'

Her own fantasies include:

Says Annabel, 'Kindness can build on itself as much as violence can.'

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

In Melbourne, a man might plunk a coin into a stranger's parking meter just in time.

In Perth, a dozen people with pails and mops and tulip bulbs might descend on a run-down house and clean it from top to bottom while the frail elderly owners look on, dazed and smiling. In Brisbane, a teenage boy may be mowing the lawn when the impulse strikes. What the hell, nobody's looking, he thinks, and mows the neighbour's lawn too.

It's positive anarchy, disorder, a sweet disturbance. A woman in Darwin writes 'Merry Christmas!' to the tellers on the back of her chechs. A man in Sydney whose4 car has just been rear-ended by a young woman, waves her away, saying, 'It's a scratch. Don’t worry.'

Senseless acts of beauty spread: A man plants daffodils along the roadway, his shirt billowing in the breeze from passing cars. In Mount Druit, a man scrubs graffiti from a green park bench.

They say you can't smile without cheering yourselve up a little - likewise, you can't commit a random kindness without feeling as if your own troubles have been lightened if only because the world has become a slightly better place.

And you can't be a recipient without feeling a shock, a pleasant jolt. If you were one of those rush-hour drivers who found your bridge fare paid, who knows what you might have been inspired to do for someone else later? Wave someone on in the intersection? Smile at a tired clerk? Or something larger, greater? Like all revolutions, guerrilla goodness begins slowly, with a single act.

Let it be yours.