Dentists should help their patients to prevent cavities rather than waiting until cavities are present to begin treatment. A condition that is only potentially harmful should not be treated using a method that is definitely harmful. A condition that is typically progressive should not be treated using methods that provide only temporary relief. Dentists should perform any procedure that it likely to be beneficial in the long term, but only if the procedure does not cause immediate damage.
Dental researcher: Filling a cavity in a tooth is not a harmless procedure: it inevitably damages some of the healthy parts of the tooth. Cavities are harmful only if the decay reaches the nerves inside the tooth, and many cavities, if left untreated, never progress to that point. Ttherefore, dentists should not fill a cavity unless the nerves inside the tooth are in imminent danger from that cavity.
Which one of the following principles, if valid, most strongly supports the researcher's reasoning?