In his movement's newsletter These Exit Times, Mr Knight, a resident of Portland, Oregon, provides a forum for likeminded readers sharing his desire for a world where animals can live without the threat of extinction - and where civilisation is finally silent. He says he came to this point of view in his early twenties: 'I looked at the world's problems and I traced them back to a primary source: homo sapiens. No matter how much we conserve, recycle, and eat low on the food chain, we have a huge and detrimental impact on nature.' He decided to have a vasectomy and then to embark upon his life's work: to persuade mankind to phase itself out.
Though Mr Knight is reticent about VHEMT's membership figures, he is convinced that his philosophy has a big potential following out there. He is encouraged by the letters received by These Exit Times (through which readers can also send off for VHEMT badges and 'Thank you for not breeding' bumper stickers.)
In a recent issue, one member writes: 'I've always felt more attuned to other species and somewhat uneasy about being a human.' Another claims:'As far as I'm concerned, the logic of VHEMT is airtight. A few years ago, I had a vision of mankind as a candle flame with the candle voluntarily slowly extinguishing itself and going out. I think this 'sacrifice' could be considered the greatest moral act that humanity could accomplish.'
The unconverted might see one or two problems here. There is, for example, the small matter of the basic human drive to reproduce. Mr Knight is sceptical. While he accepts the existence of sexual drive, he thinks the need for children is 'cultural conditioning', and that such desires could be channelled elsewhere: perhaps into gardening, adopting a stream, caring for old people, or by having a pet. (There is a strip cartoon in These Exit Times called Bonobo Baby: its heroine eschews motherhood, and decides to raise a bonobo, an endangered species of ape sharing 99 per cent of our genes.)
VHEMT members think that their goals can be achieved by a combination of universal contraception and will-power. 'But we know we'll never see the day ourselves when no human being lives on the planet - ours is a long-range goal.'
Mr Knight has a ready answer for questions most often asked by critics. Isn't there, for instance, something uniquely valuable and precious about the human race? 'We are certainly valuable to each other but the higher up the food chain, the less important the species.'
But if VHEMT is so concerned about preserving species, surely it should also be concerned about the preservation of man? 'It would be nice to preserve the human race, but we seem to be incompatible with the biosphere.'
What about the accomplishments of the human race? How about art and science? 'Yes, but with the human race gone, we wouldn't use them. And it bothers me more that with us around there will soon be no more large mammalian carnivores. The plays of Shakespeare and the work of Einstein can't hold a candle to a tiger.'
Mr Knight has got the answer to the billion-dollar question before you ask it. 'It has been suggested that there are only two chances of everyone volunteering to be VHEMT: slim and none. The odds may be against us, but the decision to live long and die out is still the morally correct one.'