During the next 35 years, the traditional view of the sanctity of human life will collapse under pressure from scientific, technological, and demographic developments. By 2040, it may be that only a rump of hard-core, know-nothing religious fundamentalists will defend the view that every human life, from conception to death, is sacrosanct.

In retrospect, 2005 may be seen as the year in which that position became untenable. American conservatives have for several years been in the awkward position of defending a federal funding ban on creating new embryos for research that prevents U.S. scientists from leading an area of biomedical research that could revolutionize the treatment of many common diseases. When they are honest, conservatives acknowledge that giving up some medical advances is simply the price to be paid for doing the right thing.

This year, however, that view became much more uncomfortable. South Korean researchers showed that human stem cells can be cloned by replacing the nucleus of an unfertilized human egg with the nucleus of an ordinary cell. The South Korean breakthrough poses a stark challenge to the conservative position. The possibility of cloning from the nucleus of an ordinary cell undermines the idea that embryos are precious because they have the potential to become human beings. Once it becomes clear that every human cell contains the genetic information to create a new human being, the old arguments for preserving “unique” human embryos fade away.

The year 2005 is also significant, at least in the United States, for ratcheting up the debate about the care of patients in a persistent vegetative state. The long legal battle over the removal of Terri Schiavo’s feeding tube led President George W. Bush and the U.S. Congress to intervene, both...