THE BURNED OVER DISTRICT

No one really knows the answer to that yet, but people on both sides are making their most compelling arguments now, while there is no evidence for either side.

Dr. Michael Siegel, a hard-charging public health researcher at Boston University, argues that e-cigarettes could be the beginning of the end of smoking in America. He sees them as a disruptive innovation that could make cigarettes obsolete, like the computer did to the typewriter.

But his former teacher and mentor, Stanton A. Glantz, a professor of medicine at the University of California, San Francisco, is convinced that e-cigarettes may erase the hard-won progress achieved over the last half-century in reducing smoking. He predicts that the modern gadgetry will be a glittering gateway to the deadly, old-fashioned habit for children, and that adult smokers will stay hooked longer now that they can get a nicotine fix at their desks.

These experts represent the two camps now at war over the public health implications of e-cigarettes. The devices, intended to feed nicotine addiction without the toxic tar of conventional cigarettes, have divided a normally sedate public health community that had long been united in the fight against smoking and Big Tobacco.

The essence of their disagreement comes down to a simple question: Will e-cigarettes cause more or fewer people to smoke? The answer matters. Cigarette smoking is still the single largest cause of preventable death in the United States, killing about 480,000 people a year.

Dr. Siegel, whose graduate school manuscripts Dr. Glantz used to read, says e-cigarette pessimists are stuck on the idea that anything that looks like smoking is bad. “They are so blinded by this ideology that they are not able to see e-cigarettes objectively,” he said. Dr. Glantz disagrees. “E-cigarettes seem like a good idea,” he said, “but they aren’t.”

Science that might resolve questions about e-cigarettes is still developing, and many experts agree that the evidence so far is too skimpy to draw definitive conclusions about the long-term effects of the devices on the broader population.

So both sides will be trumpeting their beliefs and the makers of the e-smokes will be making profits until the research comes in.