Ignaz Semmelweis figured out he was killing patients by going from cutting open cadavers to helping with the birth of babies. He spoke of disinfecting hands from ‘cadaver particles’ using some bleach in water. He didn’t have the right theory, but he had the right solution. People ignored him though - doctors don’t like being told they’re hurting people rather than helping. Many thousands more mothers would have died before the medical community woke up to this easy fix.