President Andrew Jackson was certain giving smallpox-laden blankets to the American Indians was the right thing to do.
Lots of folks are still sure that prior to 1492 most of the Western world believed the earth was flat.
The Chicago Daily Tribune was sure that Dewey would win the election, rather than Harry S. Truman.
Green Lantern was sure that Batman couldn’t be a real superhero because he was just a guy in a bat costume.
“The Story of an Hour” everyone was sure the husband was dead.
Sure my college crush was going to be my life partner. (Nope…)
Sure I was never going to get married.
Sure I could not have children, since the doctors said so.
Folks were sure that the earth was the center of the solar system–and the universe.
They were also sure that the body contained four humors and if those were in proportion, you would be well.
Most believed in spontaneous generation–that life came from inanimate life.