Sometime in the next decade or so, neuroscientists will likely identify the specific neural networks and activity that generate the vague but vital thing we call consciousness. Delineating the infrastructure of awareness is biology's most difficult problem, but a leading researcher like Christof Koch, Gerald Edelman, or Stanislas Dehaene could soon solve it. Science will then possess what might be called a "consciometer"—a set of tests (probably an advanced version of a brain scan or EEG) that can measure consciousness the way kidney or lung function is now measured.
Common sense, law, medicine, and philosophy have long considered consciousness a central aspect of our moral existence as human beings. The ability to precisely detect and measure it promises to alter our struggles with both end-of-life decisions, like those at issue in the Terri Schiavo case, and beginning-of-life decisions involving abortion. In both instances, religious conservatives probably won't be happy about the results.
The close association of consciousness with life dates only to the last half-century, when doctors learned to sustain heart and lung function long after awareness and will were gone. In the 1980s, legislators responded by establishing whole-brain death as the legal standard of death. At the same time, upper-brain death—the cessation of organized activity in the "thinking" cortex—became a common point at which to authorize the withdrawal of medical treatment. In theory, you can pick any state of health—upper-brain death or paralysis, for example—as your own signal to stop medical care. (Read an intensive-care doctor's description of what happens when there's no such signal.) But in practice most people choose the lack of demonstrable consciousness that doctors call a persistent vegetative state.
The many judges who heard and reviewed Terri Schiavo's case thus focused first on whether she had expressed a desire to end life support if she were in such a state and then, once that was proved, on whether she was in that condition. In a strict legal sense, Schiavo's state of consciousness mattered only because she had apparently designated its loss as the signal to end her life support. In the many appeals of the trial court's decision to remove her feeding tube, however, state and federal courts repeatedly based their decisions on Schiavo's cognitive status, making it the central issue in the case. Congress and the Bush administration similarly framed their efforts to restore Schiavo's feeding tube. And here lies the affair's great irony: Religious conservatives want the law to define life as the existence of a single living cell containing human DNA. Yet their Schiavo campaign bolstered both the acceptance of consciousness as the boundary between life and death and the authority of neuroscience to measure it.
The consciometer will strengthen this authority further. Families won't have to agonize over whether an unresponsive loved one is conscious; the consciometer will tell them. People filling out living wills will be able to specify their wishes based on measurable levels of conscious function. Ethical and legal precepts will rest on a clearly defined framework. Most people may welcome an end to torturous end-of-life ambiguities; religious conservatives probably won't.
The consciometer may also profoundly alter the abortion debate in ways the religious right won't like. Abortion law has long used consciousness as an indicator, if sometimes indirect, of the beginning of morally significant human life. As the Supreme Court noted in its review of abortion-law history in Roe v. Wade, "quickening," or the first clear fetal movement at about the 16th to 18th week of pregnancy, divided legal abortions from illegal ones until the 19th century. The idea was that quickening suggested willful, independent action consistent with consciousness and reflecting the animation of the soul.
Roe replaced the quickening marker with one based on fetal viability, which typically occurs at about the 23rd week. Before that, the court ruled, abortion is a private matter concerning doctor and patient, while after that point the state has an increasing say. The court's abandonment of quickening was essentially a tactical move. Seeking more solid practical ground on which to base the law, the seven-justice majority exchanged a vague indicator of consciousness (quickening) for a more concrete developmental stage (the baby's ability to live outside the womb).
But now, scientists are getting a better grip on consciousness even as viability is becoming mushier, moving up in the second trimester as medical improvements keep alive ever-younger premature babies. This volatility (and the health problems of tiny preemies) makes viability less attractive as a legal marker. The consciometer, on the other hand, will offer firmer, more stable physiological criteria to determine the start of morally significant human life—the clear dividing line that courts have long sought. And the line will be drawn farther along into pregnancy. As leading neuroscientist Michael Gazzaniga, a member of President Bush's Council on Bioethics, describes in his book The Ethical Brain, current neurology suggests that a fetus doesn't possess enough neural structure to harbor consciousness until about 26 weeks, when it first seems to react to pain. Before that, the fetal neural structure is about as sophisticated as that of a sea slug and its EEG as flat and unorganized as that of someone brain-dead.
The consciometer may not put the abortion issue to rest—given the deeply held religious and moral views on all sides, it's hard to imagine that anything could. But by adding a definitive neurophysiological marker to the historical and secular precedents allowing abortion in the first two-thirds of pregnancy, it may greatly buttress the status quo or even slightly push back the 23-week boundary. There is another possibility. The implications of the consciometer could create a backlash that displaces science as the legal arbiter of when life ends and begins. Such a shift—a rejection of science not because it is vague but because it is exact—would be a strange development, running counter to the American legal tradition. Should a fundamentalist view of life trump rationalist legal philosophy? Roe v. Wade considered this question explicitly and answered no. For nonfundamentalists, that probably still seems right.