I mentioned Semmelweiss in my previous post. Here is a link to a Wikipedia article about him:
In brief, Ignaz Semmelweiss was a Hungarian doctor in the Vienna General Hospital, appointed in 1846.
There were three categories of maternity patients in the hospital: those who had given birth before they were admitted to hospital, those who gave birth in hospital, cared for by midwives and those who gave birth in hospital and were cared for by doctors.
Puerperal fever (which we now know to be an infection caused by bacteria) is now practically unknown in advanced societies. In the Vienna General Hospital it was common: less so in the first group, more so in the second group and alarmingly so in the third group.
Why should the patients who enjoyed the care of professionally trained doctors be more likely to contract the condition than those cared for by less expensively educated midwives (and much more likely than those who received no professional care)?
Semmelweiss proposed an explanation. He observed that the lethal doctors spent some of their time conducting autopsies and some of their time delivering babies. They wore the same clothes for both duties. They did not wash their hands after cutting up corpses and before entering the delivery room. He suspected that they might be carrying "cadaverous material" (what we now call infectious agents, bacteria etc), which caused the deadly fever.
He followed the practice of washing his hands with chlorinated lime. This is essentially the chlorine bleach we use to disinfect toilets. He begged his colleagues in vain to follow his example. His patients died in far smaller numbers than those of other doctors in the hospital, who continued to sneer.
Twenty years later Louis Pasteur, following on from Semmelweiss' observations and practices, developed the Germ Theory of Disease, without which you might never have come into existence.
Semmelweiss flourished (if you can call it that) only a century and a half ago. Has humanity (or society) come so far since then that reliance on "received wisdom" or "current theory" is never at risk from good observation and careful theorising? Nope.
I once had a conversation with a nurse about AIDS. She said I was wrong and clinched it by telling me that she had been on a special AIDS course. It was useless to point out that if the ruling theory was wrong, "trained" people (like her) were the least likely to get it right.
I'd like to see this quotation from Oliver Cromwell prominently displayed in every place of scientific education
"I beseech you, in the bowels of Christ, think it possible you may be mistaken."