The Declaration of Independence was mere words, only a piece of paper: "We hold these truths to be self-evident, that all men are created equal, and are endowed by their Creator with certain unalienable rights, that among these are Life, Liberty and the Pursuit of Happiness."

Words like these can change history while they resonate in men's minds, but can also be rendered impotent in an instant, when we close our hearts and minds to their meaning. For the equality of human beings is (as the declaration acknowledges) a secular expression of a sacred belief. The surface reality is that some people are stronger, richer, and more beautiful, able, powerful, useful and desirable than others.

It is thus always surprisingly easy to degrade the status of some human beings to the point where we lose the horror of killing them. That was the first of many disturbing reflections I received from an important new book, "The Case Against Assisted Suicide" (Johns Hopkins University Press, $49.95), edited by Dr. Kathleen Foley, one of the nation's premier pain and palliative care experts, and Dr. Herbert Hendin, a psychiatrist at New York Medical College and a leading suicide expert.

Back in 1942, for example, the distinguished American Journal of Psychiatry saw fit to publish the following professional recommendation: "I believe when the defective child shall have reached the age of 5 years ... I believe it is the merciful and kindly thing to relieve that defective -- often tortured and convulsed, grotesque and absurd, useless and foolish, and entirely undesirable -- of the agony of living." Note the language dignifying the doctor who kills and dehumanizing the patient to be killed. You will hear this language over and over again. This is the way advocates of killing people talk.

The reaction against the Nazi practice of deeming life unworthy of living halted this kind of professional discourse. But only temporarily. Today a distinguished Princeton professor of something called "bioethics," Peter Singer, explicitly rejects the declaration that all human beings have rights: "The right to life is not a right of members of the species Homo sapiens; it is ... a right that properly belongs to persons. Not all members of the species Homo sapiens are persons." Babies can be killed if parents want it. Romans believed that too, before Constantine's conversion.

In the Netherlands, one out of 20 Dutch who die is killed by a physician. After killing so often, you lose the horror of it. Half of Dutch doctors have no problem suggesting to patients that being killed might be a good idea. More than 1,000 Dutch patients each year are killed by doctors without the patient's consent. One Dutch woman with breast cancer who said she did not want euthanasia was killed anyway because, in the doctor's words, "It could have taken another week before she died. I just needed this bed."

Yet research shows that most patients requesting suicide are depressed or suffering from poor management of their symptoms, and when offered good palliative care recover a sense of meaning and dignity facing death.

But the most telling new thing I learned in "The Case Against Assisted Suicide" is the culture of silence imposed on doctors in Oregon (which legalized assisted suicide). A section of the law forbids professional medical associations or health-care providers (including individual doctors and nurses) from censuring doctors who participate (or refuse to participate) in assisted suicide.

Is killing a patient ever a proper medical function? Oregon's assisted suicide law forbids professional medical organizations from even considering this question. To care and to kill become semantically and morally indistinguishable, two types of medical procedures. In this and a hundred other ways, a right to die becomes both a right to kill and a duty to get out of the way.