You’re busy, productive, gathering information—but somehow clarity isn’t improving. The information keeps piling up, but you’re no closer to a decision. Sometimes, the problem isn’t that you’re not working hard enough. It’s that you haven’t got a process for how to test your assumptions before committing time and resources to them.

Why untested assumptions are expensive

My wife and I spent months house hunting after moving from South Africa to the UK. We’d built elaborate spreadsheets tracking mortgage rates, calculated investment withdrawals, explored borrowing options. Every week we tried to answer the same question: “How can we afford these houses?”

We thought we had a financial problem. But we actually had an assumption problem.

Four years after leaving a larger home in South Africa, we’d assumed we needed comparable space. We weren’t deciding whether we needed that much space—we’d already decided. Now we were just trying to make the numbers work. Every search parameter reflected this belief. Every viewing reinforced it. House size correlates with cost, so the bigger our assumption, the bigger our problem.

The assumptions went deeper than we realised. Even when we questioned the house size, we discovered another assumption hiding underneath: that we needed space for everything we’d brought over from South Africa. We hadn’t questioned whether we still needed or wanted those things. Two assumptions, stacked on top of each other, keeping us stuck.

How to test your assumptions (before they cost you)

Here’s the method that changed everything for us. Researchers call this process testing the null hypothesis—actively looking for evidence that contradicts your working theory rather than confirms it. Scientists use it to avoid fooling themselves but it works just as well for the kinds of everyday decisions we all have to make.

Step 1: Write down what you currently believe

Make it explicit. For us, it was “we need a house comparable in size to what we had before.” You can’t test what you haven’t articulated and the act of writing it down often reveals how shaky the foundation actually is, and how firmly your assumption is embedded in your reasoning.

Step 2: Ask “what if I’m wrong about this?”

Generate 2-3 alternative explanations that would require completely different approaches. Not “what are the downsides of my current plan?” but “what else could be true here?” For us: Maybe we don’t need that much space. Maybe we’re holding onto belongings we don’t actually want or need. Maybe our life in the UK requires different infrastructure than our life in South Africa did.

Step 3: Test one key assumption actively

Instead of waiting for contradictory evidence to appear, deliberately seek it out. We grabbed a measuring tape and went through our rental, measuring everything we actually needed space for. Then we measured the houses we were viewing. It turns out the footprint we actually needed was significantly smaller than what we’d been looking at.

From there everything changed: more housing options opened up, the numbers worked better, we were less stressed.

What this looks like in practice

You might be thinking, “But I am being thorough—I’m reading multiple sources, considering different angles.” That’s what I thought too. But there’s a difference between collecting information and testing your beliefs.

Here’s how to tell if you need this: You’ve been researching for weeks but clarity hasn’t improved. All your information keeps pointing the same direction. Someone questions your approach and you feel defensive rather than curious. You’re busy and productive but you’re not any closer to actually making a decision.

The pattern looks like diligence and feels like progress. But you’re not testing your assumptions—you’re confirming them.

Before your next research session, use this method to test your assumptions: write down what you currently believe, generate alternatives that would require different approaches, then actively look for evidence that would prove you wrong. Not evidence of downsides you can work around, but evidence that would make you abandon your current approach entirely.

Either you’ll find it—saving yourself from months moving in the wrong direction—or you won’t, and now you’ll have genuinely tested your assumption rather than just collected supporting evidence.

The confidence you gain isn’t from having researched extensively. It’s from having tried to prove yourself wrong and not being able to. That’s the difference between collecting information and thinking systematically.

This assumption-testing method is one of several practical tools you’ll find in my upcoming book, Scholar: Making sense of our complex world. It’s for anyone needing to make complex decisions outside their formal expertise—whether you’re evaluating AI tools for projects, researching schools for your children, or building credibility in a new field.

Sign up for my newsletter to get updates on the book launch, plus more practical tools for thinking systematically about the decisions that matter.