“It ain’t what you don’t know that gets you into trouble.
It’s what you know for sure that just ain’t so”
-Falsely attributed to Mark Twain
Have you ever been certain that you were right about something only to realize later (perhaps when new evidence emerged) that you were wrong? Certainty is wonderful. It can stiffen spine and strengthen your resolve, but it can do nothing to make you more right.
In reality, you are right if you are right. Truth exists regardless of how you feel about it. If you are wrong, but certain that you are right, you are still wrong. You do not escape the consequences of being wrong just because you were convinced you were right. Such certainty is dangerous. It killed two U.S. Presidents.
George Washington Was Killed by Certainty
When George Washington was 67, he was home at his plantation, Mount Vernon. After riding along in a mix of rain and sleet to check on his estate, he awoke the next morning with a sore throat. By the following day, he was having difficulty breathing. Three doctors were summoned. Implementing the standard medical treatment at the time, they initiated multiple rounds of blood letting. The idea was to release the “bad humours” that were trapped in the body. The treatment had been in practice since the Greeks and the Romans. In hindsight, however, we know that the physicians probably hastened his death.
They were wrong. Their certainty about the practice couldn’t shield even the greatest man in the country from the consequences of their error.
James Garfield Was Killed by Certainty
Eighty-two years later, as president Garfield lay recovering from a would-be assassin’s bullet, medical technology had advanced. Bloodletting had been debunked over the previous decades. Joseph Lister had stumbled upon his germ theory, but it was not yet widely embraced by the medical community. It was positively denigrated by his attending physician, Dr. Willard Bliss. Bliss was a friend and a doctor of some renown, but he did not listen to the counsel of other doctors.
The bullet was not life-threatening, but the surgery turned out to be. Garfield may have recovered if not for the infection he acquired as Bliss searched for the bullet. Alexander Graham Bell created a rudimentary metal detector to try to find the bullet. Others created the experimental air conditioning to comfort Garfield while he lay in bed. It was all to no avail. Garfield was overpowered by infection because Bliss used unsterilized instruments. He used unsterilized instruments because he did not subscribe to Lister’s new theory. In Destiny of the Republic, Candice Millard explained:
Not only did American doctors not believe in germs, they took pride in the particular brand of filth that defined their profession. They spoke fondly of “good old surgical stink” that pervaded their hospital operating rooms, and they resisted making too many concessions even to basic hygiene. Many surgeons walked directly from the street to the operating room without bothering to change their clothes. Those who did shrug on a laboratory coat, however, were an even greater danger to their patients. They looped strands of silk sutures through their buttonholes for easy access during surgery, and they refused to even wash their coats. They believed that the thicker the layers of dried blood and pus, black and crumbling as they bent over their patients, the greater the tribute to their years of experience.
Bullets did not kill President Garfield; his physician did. He was certain that he was right. His bloody lab coat would tell you just how much he knew about medicine, but certainty is not truth.
What About You?
What beliefs about your business may be preventing you from getting where you are trying to go? What do you depend on for certainty? Your education? Your experience? Your bank account?
Are you humble enough to know that you don’t know it all? Do you welcome new information? What are you certain about that you might want to rethink?

End Notes
Shepherd, A. (2015). “It ain’t what you don’t know that gets you into trouble,” which must be why The Big Short opens with a fake Mark Twain quote. New Republic. Retrieved from https://newrepublic.com/minutes/126677/it-aint-dont-know-gets-trouble-must-big-short-opens-fake-mark-twain-quote
Millard, C. (2011) Destiny of the republic: A tale of madness, medicine, and the murder of a president. New York: Double-day. (p. 157).