IN ITS FINAL REPORT, a presidential commission on medical ethics has declared that the society has a moral obligation to ensure that all its citizens have access to an adequate level of health care. This is at once a modest and a radical statement. It is modest in that it does not assert a constitutional or legal right to health care or even direct that large governmental expenditures be made. It is radical in that it calls into question the fundamental way in which this country organizes and pays for its health care.

The United States now devotes more than 10 percent of its GNP to health services. For this money, most Americans receive very good care, and a few benefit from technological advances that extend their lives at enormous cost. Yet, as the commission observes, more than 30 million Americans lack the means to obtain even the most basic types of health care, and their lives are shortened as a result.

Government subsidies through Medicare and Medicaid have enabled many lower-income people to obtain medical services affordable only to the wealthy or to middle-income people with very good medical insurance. The people who get left out tend to live in rural or inner-city areas where health care is scarce at any price or falls outside of welfare's preferred categories. Families with both parents present, for example, don't qualify for Medicaid help at all in many states; in others, they are excluded if the father has a low- paying job. People without kids are generally out of luck unless they are aged or totally disabled.

It's not easy to even out access to health care in a country where the entire system has been constructed on the notion--if not the reality--of a private health care market. Federal, state and local governments pay--directly or indirectly--more than 40 percent of the nation's health bill, with much of this subsidy flowing to upper-income people through the tax system. But government has little control over the type, quality and price of health care. Most decisions are made by patients and doctors, with the doctors, because of their near-monopoly on medical information, having far stronger say.

As a result, when government has tried to help people buy better health care it has often ended up paying a very high price for not very good care. In fact, by some measures, the nation as a whole doesn't get much for its health care dollar--Great Britain spends only about half as much of its GNP on health care, yet scores much better on general measures of national health. The commission doesn't tell the nation how to go about changing its health system, but it makes a point worth thinking about whenever health care reforms are suggested: in a nation that spends over $300 billion each year on health care, it doesn't seem fair than some people should get no health care at all.