Wherever Barry Marshall is right now, he’s probably smiling. You see, Marshall has earned that savory satisfaction that comes with being able to justifiably say ‘I told you so’. And this is no playground squabble; Marshall’s (former) opponents are a worldwide audience of medical skeptics who doubted his claim that Helicobacter pylori, a bacterium that is literally a bug, causes gastritis and ulcers in the stomach.

That was largely because Marshall’s idea ran so contrary to established beliefs (despite the fact that established beliefs never hinted at a cure), which were too deeply rooted for anyone to give his novel suggestion much credibility. Marshall contended that the bug infected and inflamed the stomach, a thought most researchers rejected since they considered the stomach’s environment too acidic to accommodate a living host. The culprit that Dr. Marshall discovered was Helicobacter pylori, an adaptable bacterium that lives within the layer of mucus that protects the stomach from the acid it produces. H. pylori defies the conventional wisdom that says it shouldn’t be able to grow in so inhospitable an environment: By creating a small alkaline bubble that neutralizes the surrounding acid, the bacteria can flourish.

Staunchly committed to his theory, however, Marshall willingly swallowed a sample of the bacterium that he had extracted from a patient of his. It contained Helicobacter pylori, so if it generated gastritis, a nauseating and often painful inflammation of the stomach, then the pathologist would have evidence of his audaciously proposed link. Marshall waited, feeling no immediate signs of the bug’s presence. Then, in the middle of the night, he began throwing up profusely – he had been right.