The Maginot Line

Following WWI, France built the Maginot Line, a massive wall of fortresses meant to stop another German invasion. The strategy rested on the outdated belief that the next war would resemble the last one; slow, trench-based and fought across fixed fronts.

But new evidence pointed to fast, mechanized warfare. Germany had tanks, aircraft, and a doctrine built on speed.

France didn’t update its priors, the initial beliefs underlying their strategy.

In 1940, Germany simply went around the Line through the Ardennes and France fell in a matter of weeks.

The Maginot Line didn’t fail because it was weak.

It failed because it defended the wrong reality.

It’s a common story in war, in life, and in business. Books have been written about the epic failures of businesses not updating their strategy in the face of new information.

Kodak - “Digital will never replace film.” As they faced the rapid growth of digital cameras.

Blockbuster Movies - “People will always want to browse movies in stores.” All the while ignoring customer backlash over return fees.

Blackberry - “Physical keyboards are essential.” Just as the iPhone and touchscreens were coming online.

Sears - “People will always prefer department stores.” While Amazon was growing over 100% per year.

The list goes on but these mistakes don’t just occur at historical scale in war or business but in our everyday decisions. We hold on to outdated beliefs that lead us astray.

Are there frameworks to help us avoid getting stuck? 

Yes, the framework was provided to us three hundred years ago by a Presbyterian Minister.

Bayesian

Thomas Bayes was an English statistician, philosopher and minister whose major contribution was a mathematical paper on probability found after his death in 1761. The resulting work became known as Bayes’ theorem. The math aside, Bayesian reasoning is a way to update a belief or prediction when provided new evidence.

A structured way of asking:

1.  What do I currently believe, ie what are my priors? 

2.  What new evidence have I received?

3.  Given this evidence, how much should I change my belief? 

Sounds relatively straightforward but we humans have all types of psychological and cognitive biases that prevent us from objectively evaluating new information.

Let’s review the most common ones.

What Often Keeps Us Wrong

Confirmation Bias

Occurs when you search for, interpret, and remember information that confirms your existing belief.

Contradictory evidence gets discounted, reframed, or ignored.

Examples in business:

• You hear the feedback from one happy customer, not the nine who churned.

• You over-weight the opinion of one sales rep who “loves the new pricing” while ignoring the rest who find it prohibitive.

Sunk Cost Fallacy

Can happen when you’ve invested considerable time, money, or emotion, making it difficult to update your beliefs.

Examples in business:

• “We spent six months building this feature, it has to be core to the product.”

• “We’ve always targeted this customer avatar, it would be too costly to shift now.”

Commitment and Consistency Bias

Once you declare a belief publicly, you feel pressure to remain consistent.

Examples in business:

• You announced a strategy months ago at the all-hands meeting, so you feel you have to defend it.

• You promised investors a plan, so updating feels like backtracking.

This is especially challenging for founders because identity and leadership image are tied to certainty.

Ego and Identity Protection

Changing a belief often requires admitting you were wrong. When those beliefs are tied to our identity they can become very difficult to change.

Examples in business:

• “I staked our future on this idea, what does that say about me if it’s the wrong one?”

• “Our company is known as the low cost provider, we can’t change that.”

Our egos are one of the strongest forces keeping us in the wrong.

Groupthink and Social Pressure

When teams bond around a shared belief, updating it requires social courage.

Examples in business:

• The “common wisdom” on the team that goes unchallenged.

• Junior employees who won’t bring contradictory evidence.

• Founders who don’t want to destabilize the team emotionally.

Anchoring

Occurs when the first number, first explanation, or first assumption becomes disproportionately sticky. That is why often in negotiations, the side to say the first number has an advantage.

Examples in business:

• Your first guess at pricing becomes “the number.”

• Your first target market becomes “the market.”

Even when new data arrives, people adjust only slightly, finding it difficult to move away from their initial experience.

How to Apply Bayesian Thinking

How do you prevent getting trapped in any number of these logical fallacies? Follow these steps:

1. Define Your Priors Explicitly

Write down your foundational assumptions. Include why you believe what you do and how you came to believe it. Note the background and context of how your beliefs came to be.

For example:

“Upon surveying our customers and performing external market research, we believe building and launching a premium tier of our product with several new features will help grow our enterprise business.”

Most of us never write these down.

If you don’t define your priors, you can’t update them.

2. Decide What Evidence Matters

Every belief or prior should be tied to pre-defined metrics.

For example:

• What enterprise growth rate achieved will be considered successful?

• How will we measure new feature acceptance and usage?

• Over what time frame should we expect to experience the growth?

Evidence doesn’t mean anecdotes. Even though the best made plans don’t evolve as we expect, having metrics that were defined ahead of time will prevent biases from creeping in.

Create metrics and review them often.

3. Build a Culture that Challenges Beliefs

Whether you’re holding yourself or your team accountable, adopting norms and rules around challenging beliefs is crucial.

You need norms such as:

• “Strong opinions, loosely held.”

• “No assumption is above questioning.”

• “We reward someone who updates early, not late.”

• “Evidence beats expertise.”

Updating priors doesn’t make you inconsistent.

It makes you accurate.

The Next Step

What are the core beliefs about your business or market that is critical to your success?

Examples could include your target customer profile, your pricing, your hiring bar, your funnel, your competitive story, anything.

Do the following with one of those beliefs:

1. Write down your belief as described previously.

2. List out where reality is currently contradicting or simply not validating your belief.

3. Finally, list what would need to be true for your belief to be incorrect.

Through this simple process you can assess whether your beliefs are as solid as previously thought or where you are at risk of being blinded by your own biases.

Start small. Update one prior.

The speed at which you correct your beliefs is the speed at which your business adapts.

And in a world that changes as fast as ours, being less wrong, faster, is a huge competitive advantage.

My goal with The Leap is to provide you each Saturday with the knowledge, tools and lessons learned to help you get started and keep going toward building your future. 

Whether you are making the leap to startups, solo-entrepreneurship, freelancing, side hustles or other creative ventures, the tools and strategies to succeed in each are similar.