Throughout your personal history, some of your biggest mistakes probably stemmed from an assumption you made that was wrong. And throughout human history in general, you can easily see the march of progress as a continual (and accelerating) discovery that one assumption after another was wrong.
The medical treatment of George Washington is a good example. You could say he died of a tragic confidence in assumptions. It started out as a sore throat. Washington had caught a cold. So he was treated with the usual procedure: Bloodletting. Why was that the usual procedure? Because Galen recommended it sixteen hundred years before, and Galen was so well-known and well-respected, and his practices and theories were so well-established, the doctors in Washington’s time assumed Galen must be right.
Of course it didn’t help. In fact, his condition got worse and he began having trouble breathing. He was famous and wealthy, so he was ministered by the “best” doctors. They put ground beetles on his throat to cause blisters (in order to pull out “bad vapors”). Then they gave him laxatives to purge his bowels. They also kept up the bloodletting for several days.
Not surprisingly, Washington went into a coma and then died. He died of assumption.
See the complete list of definitions: The 22 Virus Definitions.