We often need to know little more. To cure the illness, we need accurate diagnosis and effective treatment. To prevent an illness we must understand the whole complex system that leads to the disease. Then we can act effectively, without causing harm of some other kind. Of course, nurses and surgeons benefit from theory.
Deep understanding makes every action safer and more effective, and leads to improvement.
So we often find that the theory involved in treatment seems more concrete, and has more appeal, than the abstract theory of positive health. Prevention takes time The lung cancer patient may do better if he stops smoking, but most of the damage has been done. Prevention should start when the patient is healthy. This causes difficulty in two ways. Even when we know how to prevent an illness, we have to cope with the problems already caused.