Least of all on April 15 do most Americans have reason to doubt the truth of Ben Franklin's dictum that in this world nothing is certain but death and taxes. The Quinlan family, of Wantage, N. J., cannot share that certainty, however. Ten years ago today their daughter, Karen Ann, stopped breathing and lapsed into the coma from which she has never emerged.

After some months her family reluctantly concluded that further treatment was not justified because Karen was never going to recover. But when they asked the physician and hospital to remove the respirator that was believed necessary for her survival, the physicians said that to give up on a patient in that way would contradict medical standards. Furthermore, the care-givers feared civil and criminal liability.

When Joseph Quinlan applied to the New Jersey Superior Court to be appointed Karen's guardian, with authority to order all treatment ceased, his daughter's plight became a matter of front-page news. Yet for a "landmark" case, the court's holding has had few direct legal consequences, though it has reverberated throughout society in many important ways -- generally to good effect.

Many people say the case "defined death." It did no such thing. The coma in which Karen lies is a living state, however much some people may say that this 31-year-old, 65-pound, unresponsive patient curled in a fetal position in a nursing home bed is "dead." The fact remains that she survives without mechanical support because the portion of her brain responsible for such basic activities as respiration is still functioning. Thus she is not and never was dead according to medical standards, nor under the laws adopted in nearly 40 states as a result of developments separate from her case.

Karen's situation was often raised in the debates in the California legislature in 1976 as justification for the "Natural Death Act," which was intended to let people specify that no heroic measures be used when they are diagnosed as having a terminal condition. Ironically, the actual legislation -- since followed in about 20 states -- would not apply to patients such as Karen Quinlan, even when she was on the respirator, since the laws require that death be imminent whether or not life-sustaining procedures are used.

The New Jersey court also urged hospitals to appoint multidisciplinary "ethics committees," a concept that has been much discussed of late and promoted by the federal government in its "Baby Doe" regulations. Yet at the time of the actual Baby Doe case two years ago, only about 1 percent of American hospitals had such committees. Perhaps it was because the actual task assigned by the court to the committee in the Quinlan case (simply to review the attending physicians' prognosis that Karen wasn't going to regain cognitive functioning) was too narrow to seem attractive to physicians and hospital administrators.

Many people believe the Quinlan decision adopts a pro-death, anti-treatment standard for the law. This conclusion may be abetted today by society's growing awareness of the "high cost (to the rest of us) of (other people's) dying." In fact, the Quinlan case simply made it plain that society does not expect physicians to go on endlessly with treatment that is not curative, and that respecting the wishes of patients -- or their best interests, when their exact wishes are not known -- does not expose physicians and hospitals to legal liability.

Karen may survive another 10 or 20 years because her parents believe that artificial feeding is appropriate while an artificial respirator was not. Even though many of us would disagree, their decision falls within the court's holding in her case. Indeed, it is at the heart of the Quinlan holding, because the court recognized that such decisions should be guided by personal moral choice, not wooden rules. In each case the question is: Does the patient (or patient's surrogate decision-maker) believe that this treatment offers a reasonable prospect of benefit, in light of the burdens.

Paradoxically, Karen Quinlan, through a tragedy that left her silent and unable to exercise choice, became in effect a teacher to millions, provoking a reexamination of personal and professional goals and assumptions in homes and hospitals, in medical schools and in legislative chambers.

The reaction to her case helped to break the lock of medical technology that had gripped physicians and patients alike, and prompted hospitals to introduce procedures more responsive to the wishes of patients and families. More important, it provoked a broad public debate about the appropriate uses of and limits to our ever-growing array of medical technology. That debate is still going on.