"The cure for the greatest part of human misery is not radical but palliative," Dr. Samuel Johnson, who was never at a loss for words, said in 1750. He could have been speaking of medicine today.

More than 200 years later, despite the flood of dramatic developments in medicine, new diagnostic tools and sophisticated forms of therapy, there are still many diseases we cannot cure but must deal with by relieving symptoms. For heart disease, most cancers, stroke, rheumatoid arthritis and a host of other major illnesses, physicians have to settle for making patients more comfortable and helping them live with their medical problems.

The limited ability of doctors to reverse disease is at odds with the public's increasing demand for a total cure. At the beginning of this century, physicians acknowledged that very few treatments were sound. Digitalis helped in cases of heart failure, quinine stopped malaria, aspirin relieved aches, and morphine deadened pain. The doctor's job was to figure out what disease the patient had, explain it to family members, and tell them how it was most likely to turn out. Often he waited at the bedside to "see them through" their disease and announce to the family that the crisis was over, one way or the other.

But in the last generation medicine has become a therapeutic profession. The arrival of powerful antibiotics, medicine's new-found ability to treat endocrine and nutritional disorders, and many new surgical techniques have combined to inflate the physician's role in the public eye. Today the patient no longer asks, "What is my problem and what can I expect?" but instead, "What are you going to do about it?" The physician then becomes frustrated when confronted with a disease he cannot cure.

Consider multiple sclerosis, a disabling chronic disease of the central nervous system with no known cause or cure. In earlier times, doctors often withheld confirmation of the diagnosis from patients. Now the pendulum has swung the other way. Patients are demanding to know what they have, and doctors are tending to tell them. This has brought on "premature diagnosis." Pressure for early diagnosis is pushing many doctors into a corner, and sometimes they're making fast and imperfect decisions.

To be sure, it's a lot easier to give a quick diagnosis than to say candidly to the patient, "You are showing these symptoms and I don't know exactly what they mean. You and I are going to have to live with uncertainty for a while. A slew of tests may not be helpful. Call me if anything new happens. In six months I'll reexamine you."

I would have more faith in a doctor who takes that approach than in one who gives an immediate diagnosis of multiple sclerosis.

Yet everyone wants to name the problem.

New tests are paving the way to faster, more accurate diagnoses, but new problems arise. The method of mapping internal tissues called magnetic resonance imaging, for example, is very sensitive at pinpointing multiple sclerosis lesions that cannot be seen in any other way. But what if a patient with a severe migraine is given this scan, and it shows brain abnormalities suggestive of MS? Should this person, who has shown no clinical MS symptoms, be told he has the disease or has a good chance of developing it later? The cautious doctor will not jump to a diagnosis based on magnetic resonance imaging alone; he will depend heavily -- as always -- on history-taking and physical examination.

Patients are always interested in new therapies, which is natural. This poses no problem as long as the agents taken are harmless. But some new drugs are potentially very dangerous. They should not be prescribed lightly; in fact, potent drugs really should be given only under the umbrella of a carefully designed clinical trial that defines the severity of disease justifying their use.

In the case of multiple sclerosis, more and more patients who are seeing a doctor for some minor symptom that might respond well to physical therapy or a muscle relaxant but instead are being put on a powerful immunosuppressive drug whose long-term effects are not known. A patient with a chronic disease such as multiple sclerosis has a life expectancy 30 or 40 years, during which time a toxic drug could have very severe effects.

Even totally harmless therapy can be devastating from an economic viewpoint. For example, some MS patients claim a regimen of hyperbaric oxygen therapy -- sitting in a chamber breathing pure oxygen at twice atmospheric pressure for 90 minutes -- helps their urinary tract symptoms. This is well and good if it works; but HBO costs about $100 a treatment.

People need to understand that there are no magical cures or white-coated mandarins who can make a very complex disease disappear overnight. They need to find a doctor they can trust, stick with him, and not push him into premature diagnoses or quick fixes.

Cures will come. Research seems slow, but progress is being made by dedicated scientists working at reputable laboratories. When the word is out on a new treatment that really works, doctors and public will know about it very quickly. Until then, some of the tried-and-true formulas are probably our best hope of controlling symptoms and keeping life as close to normal as possible.