IN THE AFTERMATH OF THE Terri Schiavo case, it seems clear that most Americans are uncomfortable at the prospect of politicians' intervening in family decisions about life and death. This is not only understandable, but usually wise. Americans understand that eventually they will have to make medical decisions for loved ones, and that such decisions are wrenching. Most people have little faith that the state--or the courts--can make better judgments than they can. And they are usually right.

But it is precisely the complexity of these life-and-death decisions that sometimes makes state involvement inevitable. The state was involved in the Schiavo case long before Congress intervened, from the time Terri's parents went to court in Florida to challenge her husband's fitness as a guardian back in 1993. State judiciaries must decide when family members clash, or when doctors and families disagree, or when surrogates wish to override a loved one's living will. And state legislatures have a responsibility to set the parameters for judicial decisions in particular cases. They must decide the admissibility of casual conversations in determining a person's prior wishes, or the appropriate weight to give a person's desires (such as requests for assisted suicide) even when they are clearly expressed.

For decades, we have deluded ourselves into believing that living wills would solve our caregiving problems; that healthy individuals could provide advance instructions for what to do if they became incompetent; that such a system would ensure that no one is mistreated and that everyone defines the meaning of life for himself until the very end. But it is now clear that living wills have failed, both practically and morally.

In the March-April 2004 issue of the Hastings Center Report, Angela Fagerlin and Carl E. Schneider survey the social science data, and their conclusions are damning: Most people do not have living wills, despite a very active campaign to promote them; those who do usually provide vague and conflicting instructions; people's opinions often change from experience to experience; and people's instructions are easily influenced by how a given scenario is described. These are not problems that any reform can fix. A person simply can't grasp in the present every medical and moral nuance of his own future case.

The dream of perfect autonomy--everyone speaking for himself, never deciding for another--should fade each time we change a parent's diaper, or visit a grandparent who does not recognize us, or sell an uncle's property to pay for the nursing home. After all, the only fully autonomous death--with every detail governed by individual will--is suicide. And suicide is hardly a basis for dealing more responsibly with the burdens of caregiving.

As the baby boomers age, we are entering a period when long-term dementia will often be the prelude to death, and when caregivers will regularly have to make decisions about how or whether to treat intervening illnesses like infections, heart trouble, or cancer. When should we accept that death has arrived, and when does stopping treatment entail a judgment that Alzheimer's patients are "better off dead"? What do we owe those who are cognitively disabled and totally dependent?