Abraham Wald was the founder of operational research. What set him apart though was that he could see the invisible bullets.
During World War II, the US was losing several bombers to enemy fire. On examining the surviving planes, researchers on the ground noticed that some regions of the planes had more bullet holes than others. Therefore, they concluded that these places needed additional armour, given how they were susceptible to enemy fire.
But Abraham Wald rubbished this idea and suggested that they do the opposite. He asked that the parts of the plane that did not have bullet holes be armoured. He reasoned how those were the spots where the planes that had been destroyed were hit. While his colleagues had only used the surviving planes to draw their conclusion, Wald considered the ones that were more important – the planes that had crashed and the invisible bullets that had hit them.
Our brains tend to focus on whatever is visible – out of sight is out of mind. But sometimes this could lead us to the wrong conclusions. Sometimes, what you do not see is what matters the most.