LAST week's embryo-politics show brought back memories of a great philosophical textbook, Star Trek. "Emotions are alien to me. I'm a scientist," Mr Spock would say without a flicker of a smile. And Captain Kirk would shake his head at the incapacity of his Vulcan sidekick to comprehend the simple experience of being human. Even in deep space there were debates about personhood.

Autistics such as Spock find it hard to distinguish people from things - rather like the Prime Minister and premiers at last week's Council of Australian Governments meeting, which authorised the use of surplus in-vitro fertilisation embryos for research. All John Howard needed was pointy Vulcan ears when he said: "I can't for the life of me see a moral difference between that [thawing the embryos] and the use of embryos in research."

The embryo debate proves that personhood is fragile. During the past 100 years, Jews, gypsies, blacks, homosexuals, counter-revolutionaries and Albanians have all been regarded as non-people unworthy of human rights. If these horrors have taught us anything, it is this: When personhood comes in many shades of grey, someone is going to get a raw deal.

For ethical autistics, humans are puzzling. Some are people; some are potential people; some used to be people. Vulcans have to carry around checklists of humanity-defining features such as size, self-consciousness, independence, and recognisable human shape. Embryos don't make the grade. This breaks with Australia's democratic traditions. We have always stood squarely with the humanism of Star Trek. In the words of "Bones" McCoy, the starship's doctor: "A thing? Why is something we don't understand always called a thing?"

Humans are what they are because of an unchanging nature that underlies changing appearances. You can no more have partial humanity than a partial triangle. There is no such thing as a pre-person stage of human life. Personhood begins at conception and lasts until death.

This is why the COAG meeting was so significant. For the first time, we have endorsed a Vulcan view of human nature as a checklist instead of an unchanging, constant, unified whole. This revolution has drawbacks that must be highlighted when the embryo bill goes before parliament.

The most obvious is that humanity and human rights have become negotiable. The embryo does not have enough ticks, so it will not be regarded as a person. In Spock's famous words: "It's life, Captain, but not life as we know it."

What about other humans without enough ticks, such as deformed babies or comatose patients? Vulcan philosopher Peter Singer has clear and simple ideas of what can be done. Is Howard prepared to tag along? And who ticks the boxes? Who will set the criteria for personhood or for what constitutes a worthwhile life?

So human life is now a source of profit. NSW Premier Bob Carr has compared IVF scientists with Galileo, but there is a difference: Galileo didn't have stock options.

If you want to peer into our future as a fully fledged Vulcan colony, look at China. Even ethically autistic politicians might have misgivings if they knew what is happening there.

Executions are the main source of organ transplants in China according to The New York Times. Last year, the 10,000 people put to death were put to good use - without their consent. Kidneys, livers, lungs, corneas and other organs were stripped from the prisoners and transplanted into wealthy patients. Like research on surplus embryos, this is a thrifty use of material that would otherwise be discarded.

China permits research on four-week-old embryos. The Wall Street Journal recently reported that Chinese scientists have cloned human embryos. Others have used rabbit egg cells to create them. "Eventually the fusion could lead to the development of a hybrid animal," said one of the scientists.

Could Australian ethical standards slip this low? Quite possibly. Earlier this month the vice-president of the Australian Medical Association, Trevor Mudge, defended stem cell research by asserting that "respect for human life is not an absolute". If Vulcan doctors abjure their Hippocratic oath, who can tell where we will end up?

Australians will be safer if they stick to the absolute value of human life at all stages of its cycle. To quote Kirk (Stardate 5431.6): "No one may kill a man. Not for any purpose. It cannot be condoned."

Michael Cook is the editor of Australasian Bioethics Information.