Lesson Content

Why unchallenged assumptions are costly.

Every plan, every decision, and every strategy is built on assumptions. Most of them are never examined. You assume the market will respond a certain way. You assume the technology will work as described. You assume your team has the capacity. You assume the timeline is realistic. When those assumptions are wrong – and they often are – plans fail for reasons that were visible in advance but never looked at.

Gemini is useful for assumption-challenging because it has no stake in your assumptions being correct. It does not need to protect feelings, maintain relationships, or avoid awkwardness. It can challenge your reasoning directly – if you give it permission to.

The assumption-extraction prompt.

The first step is to surface assumptions you are not aware you are making:

"Here is my plan/decision/strategy: [describe it]. Identify the key assumptions this plan depends on – things I am taking for granted that, if wrong, would significantly change the outcome. Organize them by: (1) assumptions I have stated explicitly, (2) assumptions I have implied but not stated, and (3) assumptions I appear to have made without being aware of them. Be thorough."

The third category – assumptions you did not know you were making – is usually the most valuable output of this exercise.

The steelman and counter-argument.

After surfacing assumptions, test them with two complementary techniques:

Steelman (the strongest version of your position):

"Make the strongest possible case FOR my plan, assuming all my assumptions are correct. What would make this plan excellent?"

Counter-argument (the strongest case against):

"Now make the strongest possible case AGAINST my plan. Assume you are a skeptical critic who has seen similar plans fail. What would cause this to fail, and what is the most important thing I have not addressed?"

The gap between the steelman and the counter-argument reveals the most important uncertainties in your plan.

The "what would have to be true" technique.

For decisions that feel certain, this technique is particularly revealing:

"I have decided to [decision]. What would have to be true for this to be the wrong decision? List the conditions under which this decision fails – and estimate how likely each condition actually is."

This forces an honest examination of what you need the world to be for your plan to succeed – and whether you have actually verified that those things are true.

Calibrating your response to the challenge.

When Gemini challenges your assumptions or argues the other side, the productive response is not to defend your position reflexively – it is to evaluate whether the challenge reveals a real vulnerability or a scenario you have genuinely already considered and mitigated.

Ask for each challenge: "Is this a gap I should address, or have I already considered this and why is my current approach still correct?" This prevents both over-updating (abandoning a good plan for a weak counter-argument) and under-updating (defending a bad plan with motivated reasoning).