The Tenth Man Rule: How to Break Out of Groupthink and Make Smarter Decisions
Why diverse thoughts make a difference in all areas
There’s a well-known story in military intelligence circles that I want to share today. After the catastrophic intelligence failure of the Yom Kippur War in 1973, Israeli defence officials decided to implement a new decision-making rule. If nine people in the room agreed on a strategy, the tenth person was required to challenge it, even if they believed it was correct. The idea? To Force critical thinking. Expose blind spots. Make sure the team wasn’t just nodding along to bad ideas because they sounded good.
This is known as the Tenth Man Rule, and it’s something every founder, entrepreneur, and leader should have in their playbook. Not just as a way to challenge consensus thinking, but also as a reminder to be open to feedback and avoid doubling down on a bad idea because of ego.
Why This Matters in Business
Most startups don’t fail because the founders are dumb. They fail because of groupthink. This is where smart people reinforce each other’s assumptions and ignore warning signs until it’s too late. The best leaders balance conviction with adaptability.
There are two sides to the Tenth Man Rule:
Being the Tenth Man – Challenging the prevailing view, thinking differently, and identifying risks that others ignore.
Accepting the Tenth Man – Creating an environment where different perspectives are welcomed, not dismissed, and adjusting plans when new insights emerge.
I love the saying “Strong opinions, weakly held”. This is the idea that you should back your ideas with conviction but be willing to drop them when new data comes along. This is how the best companies operate. They move fast but adjust when the world tells them they’re wrong.
Examples of the Tenth Man Rule in Action
1. Netflix vs. Blockbuster
In 2000, Reed Hastings offered to sell Netflix to Blockbuster for $50 million. The Blockbuster execs laughed him out of the room. Their thinking? DVDs were their cash cow. Why mess with a winning formula?
They needed a tenth man in that meeting. Someone who wasn’t afraid to say, “What if online streaming isn’t a fad? What if we’re missing a shift in consumer behaviour?” Instead, they dismissed it. And now? Blockbuster is dead, and Netflix is worth over $200 billion.
2. BlackBerry’s Fall
BlackBerry owned the smartphone market in the mid-2000s. Their leadership thought touchscreen phones were a gimmick. Even as iPhones and Androids started taking over, they refused to adapt.
They needed a tenth man to say: “Maybe people will get used to typing on glass. Maybe apps are the future.” Instead, they doubled down on what had worked before. And now? BlackBerry is a relic of the past.
3. Amazon’s “Disagree and Commit” Culture
Jeff Bezos built Amazon’s culture around welcoming dissent but making decisions quickly. Teams are encouraged to challenge ideas, even if they’re the only one who disagrees. But once a decision is made, everyone commits fully.
This is the Tenth Man Rule done right. To question everything, but when a choice is made, move forward as one team.
How to Apply the Tenth Man Rule in Your Business
Want to avoid becoming the next Blockbuster? Here’s a simple framework to bring the Tenth Man Rule into your company:
1. Assign a Devil’s Advocate
Every time a big decision is being made, assign one person to argue the opposite view. Their job is to find weaknesses, explore risks, and make the team justify their position.
2. Reward (Not Punish) Dissent
If people are afraid to challenge ideas, groupthink wins. Create a culture where different opinions are encouraged, and not seen as disloyalty.
3. Ask, “What Would Make Us Wrong?”
Before making a decision, ask: “If this fails, what will have caused it?” Identifying failure points in advance makes you more prepared.
4. Conduct Pre-Mortems
Instead of waiting for things to go wrong and doing a post-mortem, do a pre-mortem. Assume the project has already failed, and then ask, “What went wrong?” This forces you to consider risks before they happen.
5. Make It Safe to Change Your Mind
Some of the worst business decisions happen because leaders feel trapped by past choices. If you made a bad bet, admit it, pivot, and move forward. Strong opinions, weakly held.
6. Don’t Just Listen to the Tenth Man… Act on It
It’s not enough to hear dissent. You have to be willing to change course when better insights emerge. If everyone ignored the tenth man, the whole rule would be pointless.
The Fine Line Between Conviction and Stubbornness
Some of the greatest companies were built by people who ignored conventional wisdom. But the best founders also knew when to change their mind.
The Tenth Man Rule isn’t about negativity. It’s about avoiding avoidable mistakes. It’s about being decisive and adaptable. It’s about thinking critically, challenging assumptions, and building a team that isn’t afraid to tell you when you’re wrong.
So next time you’re in a big meeting and everyone agrees…. pause. Assign a tenth man. And make sure you’re not just following the herd off a cliff.
How do you encourage contrarian thinking in your team? Have you ever been the tenth man in a meeting and changed the course of a decision?
Best,
Jon Butterfield
