The owners of Arnold’s apartment building think otherwise. In October 2008, Swiss television aired a documentary about Dignitas in which Arnold was shown handing a cup of sodium pentobarbital to an American man suffering from a motor neuron disease. His landlords responded by changing the locks on his apartment. Arnold was not surprised by their reaction. “There are forces that want to stop us, mostly from the religious corner,” he told me. “It’s very difficult to discuss this with them.”

Discussing this practice with anyone can be difficult, not just because of differences in religious or moral values but for the sheer range of terms used to describe it. The variations include assisted suicide; physician-assisted suicide; euthanasia by action; euthanasia by omission; passive euthanasia; active euthanasia; voluntary euthanasia; involuntary euthanasia; voluntary passive euthanasia; involuntary passive euthanasia; voluntary active euthanasia; and involuntary active euthanasia. To these, add ideological slogans like “the right to die,” “dying with dignity,” and “end-of-life decision-making.” This multiplicity of terms is the fruit of more than 2,000 years of argument, during which opinions have shifted dramatically.

Assisted suicide did not always carry the stigma it does today. It was an accepted practice in the ancient world. Athenian magistrates stockpiled poisons for their citizens, with the admonition “If your life is hateful to you, die; if you are overwhelmed by fate, drink the hemlock.” The Hippocratic Oath, written sometime between the fifth and third centuries B.C., pledged doctors to refrain from hastening the deaths of their patients and specifically prohibited the prescription of fatal drugs. The oath was a seminal development in the ethics of medicine, but was ignored by most ancient physicians. Only hundreds of years later, with the rise of Christianity and its belief in the sanctity of human life, did attitudes toward euthanasia swing decisively in the other direction. By the 12th century, mercy killing was opposed throughout the Western world. Thomas More’s Utopia, published in 1516, reinvigorated debate with its vision of a society in which “the magistrates and priests do not hesitate to prescribe euthanasia,” and where the sick “end their lives willingly, either by starvation or drugs.” Later, during the Enlightenment, thinkers like Francis Bacon, David Hume, and Montesquieu, among others, also defended the practice, though their writings did little to alter the prevailing wisdom.

The modern argument over euthanasia began only in the 19th century with the advent of medical anesthetics like ether and morphine. In 1870, a schoolteacher named Samuel D. Williams delivered a speech to the Birmingham Speculative Club in England. He argued that, for patients suffering from terminal illness, physicians should use chloroform not only to relieve pain, but to “destroy consciousness at once, and put the sufferer to a quick and painless death.” His comments were later collected into a book that received favorable attention from prestigious political and scientific journals and inaugurated a period of spirited discussion, in both Europe and the United States, over euthanasia’s potential to cure certain social ills. Scientific rationality was the byword of the age. Darwin’s theory of evolution had itself evolved into the sociological notion of “survival of the fittest.” Euthanasia promised the possibility of a healthier and more productive society, free from the burden of caring for its weakest members—the sick, the old, and the mentally ill. In 1906, two bills introduced in the Ohio legislature called for the legalization of euthanasia for terminally ill adults and for “hideously deformed and idiotic children.” They were voted down.

More failed legalization bids followed on both sides of the Atlantic. Beginning in the 1920s, German scientists led the way in Europe with the establishment of numerous academic centers devoted to eugenics, a burgeoning field of study that, among other things, promoted euthanasia as a means of eliminating physical and mental imperfections from the gene pool. The Nazis were close students of the latest theories. In euthanasia they found the ideal tool to put their policy of “racial hygiene” into action—not only to relieve human suffering, but to bring death to those they deemed “unworthy of life.” The category was broadly defined. By 1945, images from the death camps silenced further discussion of euthanasia, if only for a while.