Dingbat.
All the best people and consensus was that ulcers were caused by stress.
But you keep lying through your teeth and sliding topics.
Troll.
So?
Once upon a time, respiratory diseases were believed to be caused by "miasmas."
The fact that scientists keep researching and sometimes uncover new facts that no one knew before (like the role of H. pylori in the development of ulcers) does not at all invalidate my previous statement that science proceeds according to theory and builds on previous research.
Barry Marshall would never have been able to pinpoint H. pylori as the cause of ulcers without the work of countless scientists who preceded him in characterizing bacterial biology, identifying and verifying the role of a specific organism in causing a disease (Koch's postulates), in developing laboratory analysis methods, reagents, and equipment, etc. He wasn't just some bloke who walked in off the street without any knowledge of scientific theory and method who then pronounced that H. pylori causes ulcers.