10th man theory.

If everyone is thinking alike, then somebody isn't thinking.

George S. Patton

It's always helpful to have someone who doesn't think like everyone else. 

To avoid unwanted surprises like The Yom Kippur war with Egypt and Syria in 1973, Israel had instituted a policy known as “the tenth man.”

It goes like this:

When nine people agree on something, it’s the tenth man’s responsibility to disagree no matter how improbable the idea.

When the email came through that zombies were on their way, the tenth man proposed that they prepare for a zombie invasion, no matter how ridiculous the idea seemed.

While this is obviously an extreme example, there’s an important lesson there that you can use to avoid fooling yourself.

Prove Yourself Wrong

If the tenth man hadn’t spoken, Israel would have been overrun by zombies like the rest of the world.

The tenth man forced Israel to consider an alternative view point, something we humans usually resist.

As Michael Shermer puts it in his book The Believing Brain, the human brain is a “belief engine.”

We are pattern-seeking machines. We look for connections everywhere. We get things right a lot of times (lifting weights does help muscle growth), but we often get things totally wrong (ketosis and fat loss).

A better way to implement the “tenth man policy” would be as follows:

Whenever nine men agree on something, it’s the tenth man’s responsibility to present a case for an alternative view point — no matter how ridiculous the idea sounds.

“When you find yourself on the side of the majority, you should pause and reflect.” ~Mark Twain