Assumption Sages

“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.” - Unknown (often attributed to Mark Twain)

The "Black Swan"

Once upon a time, European explorers had only ever seen white swans. Their conclusion was simple: all swans—every single one—must be white. That assumption held. Until they discovered black swans in Australia. In a single moment, the safe assumption that had felt like bedrock, was shown to be quicksand.

More generally, assumptions are things that we accept as true or certain to happen, without proof.

The unexpected Black Swan

Why we need assumptions

To work efficiently and effectively our brains make shortcuts. To live without assumptions - for example questioning gravity with each thrown ball or doubting the sunrise every morning would be paralysing. Assumptions let us remove any uncertainty from things we feel confident about and build models of our world.

Assumptions are good right? Yes, but knowing that we are making assumptions, and calling them out, is essential to stop us sleep-walking into limiting beliefs or worse, catastrophe. The ground can shift beneath our assumptions.

Assumptions like theories and heuristics are valuable as long as relied upon sensibly.

Assumptions we make each day

1. Clean, drinking water will come out of the tap each morning

2. A piece of paper we have in our wallet, will be accepted as valuable by the shop we give it to

3. When you are shown a green traffic light, oncoming traffic is shown red, and observe that by stopping.

4. Your fridge will cool your food

Imagine a world where you had to revise these assumptions and how much more mental attention you would have to pay to everyday occurrences.

Assumptions change

Positive big change can happen when assumptions turn out not to be true:

• Wright Brothers: Disproved the belief that flight required lighter-than-air designs.

• Elon Musk: Challenged the notion that electric cars lack range

But it can also prove terrifyingly negative implications:

• Illness is caused by bad air or evil spirits: This approach was dominant in Europe for many centuries hampering medical advances.

• Women should be sheltered rather than venture outside the home: this assumption meant women were not invested in and had hugely restricted lives

• During the Global Financial crisis, an unwritten assumption was that House Prices would never go down, and that borrowers would default for different reasons. both of those assumptions were false leading to huge bank losses.

How can we handle assumptions with care?

Assumptions are powerful when used responsibly. The following table might help you test your assumptions.

Table: Questions to Ask About Your Assumptions

Stage	Question	Purpose
Spot the Assumption	- What do I believe is true without questioning it? What am I taking for granted?	Bring your assumptions to the surface.
Source & Justification	- Why do I believe this?- Is it based on evidence, experience, or a guess?- Who told me this was true? Has it ever been untrue? Can I create a scenario where this is not true.	Check how solid the assumption really is.
Impact & Risk	- What happens if this assumption is wrong?- What decisions rely on it?- Is this assumption make-or-break?	Identify which assumptions need testing.
Test or Validate	- How could I test this?- What evidence would confirm or challenge it?- Can I run a small experiment or ask someone?	Reduce risk and verify the assumption.
Adjust & Respond	- Has anything changed that makes this assumption outdated?- What would I do differently if it were false?- How flexible am I willing to be?	Update your thinking based on new information.

Of the stages, I think 1 & 3 are the most involved, as they require creativity, and imagination which are often lacking when we are having conversations about things. There are many instances where the law, social norms, circumstances or technology has changed, making things possible or impossible instantaneously.

The double-edged sword of AI and assumptions

Training models entrenches past data—and its embedded assumptions—into future forecasts. Trained on a stable period, AI can miss sudden regime shifts. Yet, when we design models to detect anomalies, AI becomes our early-warning system for shattered assumptions. In this way as in many ways, technology can only amplify our own assumptions, and will generally only find what we are asking it to look for.

Become an "assumption sage"

You heard it here first folks. A huge unlock, to allow you to become a master of assumptions rather than a passive recipient of them is to become an assumption sage. Both personally and professionally, the people who impress me most, are those that are willing to challenge assumptions.

In a world of huge, rapid change, knowing what is solid ground and what is quicksand can help you seize opportunities and avoid pitfalls. This how you as an Assumption Sage can add value to all those around you.

So what?

1. Assumptions are invisible foundations– They help us navigate daily life, but when left unexamined, they can lead to serious errors or missed opportunities. Surprising truths often come from challenging what we “know for sure.”

2. Everyday assumptions make life easier — but can lull us into complacency– From trusting tap water to traffic lights, we rely on unspoken truths — until they change. Wright Brothers generated success through challenging norms. The Global Financial Crisis was a failure from trusting faulty assumptions.

3. Assumption Sages handle assumptions with care and curiosity – Use a structured approach: Spot, Justify, Assess Risk, Test, and Adjust. The real power lies in knowing which beliefs to question — and having the courage to do it.

Next week I will be discussing "What are stories?". Until then, please sign up to receive the blog directly to your email at Blog | Deciders.