Testing Your Assumptions

You have hundreds of beliefs about how the world works. Most of them you’ve never tested. Some of them are wrong.

This isn’t an insult - it’s just math. No one has time to test every belief they hold. You picked up most of them from the people around you without thinking. You got them from your culture, your parents, your friends. And some of those beliefs are bound to be wrong.

For the beliefs that matter to your life, a little scientific thinking helps a lot.

What Scientific Thinking Actually Is

Science isn’t about lab coats or expensive equipment or credentials. At its core, it’s embarrassingly simple:

  1. Make a prediction based on your belief
  2. Look at reality to see if the prediction holds
  3. Update your belief based on what you find

That’s it. The method is trivial. The hard part is being honest with yourself about what you find-especially when reality contradicts something you really wanted to be true.

The Key Question

For any belief you hold, ask:

“What would I expect to see if this belief were wrong?”

If you can’t answer that question, your belief can’t be tested. It might still be true. But you’re not holding it because of proof - you’re holding it for other reasons (who you are, how you feel, what others think, or just habit).

Example: “My boss doesn’t respect me.”

What would you expect to see if this were wrong?

  • Your boss asks for your opinion in meetings
  • Your boss gives you challenging projects
  • Your boss mentions your contributions to others

Now you have something concrete to look for. Pay attention. Actually count instances. You might discover your belief is accurate-or you might discover you’ve been filtering out evidence that contradicts it, only noticing the slights while ignoring the respect.

The point isn’t to prove yourself wrong. The point is to find out what’s actually true.

Common Untested Assumptions

Here are beliefs many people hold without ever testing:

“I’m bad at X”

Maybe you’re bad at math, public speaking, meeting people, or writing. But have you actually tested this lately? Or are you stuck on an old story from years ago - maybe from childhood, maybe from one bad time that you turned into a permanent label?

Test it: Try the thing. Not once-multiple times, with deliberate practice. Track your actual performance, not your feelings about your performance. Feelings are not data.

“People think Y about me”

You assume people judge you a certain way. But have you asked? Have you looked for actual evidence? Or are you just projecting your fears onto other people’s faces?

Test it: Ask trusted friends for honest feedback. Watch how people actually treat you, not how you imagine they’re secretly thinking. Most people are too busy worrying about how they’re perceived to spend much time judging you.

“This relationship/job/situation can’t change”

You’ve decided something is fixed. But is that based on evidence or resignation?

Test it: Make one specific change and observe what happens. Many “unchangeable” situations change when you actually try something different. You’ve been operating under the assumption that change is impossible-but you haven’t actually tested it.

“I know why they did that”

You’ve assigned a motive to someone’s behavior. But do you actually know, or are you guessing based on how you’d interpret that action if you did it?

Test it: Ask them. Or at minimum, generate three alternative explanations for their behavior. Can you rule them out? Usually you can’t-you just picked the first explanation that occurred to you and stopped looking.

The Prediction Game

Here’s a practical exercise for testing your assumptions:

  1. Write down a prediction based on your belief. Be specific. “X will happen by Y date” or “If I do A, B will occur.” Vague predictions are useless because you can always claim you were right.

  2. Commit to the prediction before seeing the outcome. Write it down. Tell someone. Lock it in.

  3. Observe what actually happens.

  4. Score yourself honestly. Was your prediction right? Wrong? Partially right? No retroactive reinterpretation allowed.

Example:

Belief: “My coworker doesn’t pull their weight.”

Prediction: “In the next week, they will complete fewer tasks than the team average.”

Observation: They actually completed more tasks than average.

Update: Maybe your belief was wrong. Or maybe “pulling weight” isn’t about task count-maybe you need to refine what you actually mean. Either way, you’ve learned something you didn’t know before.

The Pre-Mortem

Before starting a project or making a major decision, imagine it failed. Not “might fail”-did fail. It’s six months from now, and this was a disaster. What went wrong?

This trick (called a pre-mortem) helps you find assumptions you didn’t know you had. It’s easier to see your blind spots when you picture failure than when you’re excited about success. Hope is great for staying motivated, but bad for planning.

Watch Out For These

Vague Predictions

“Things will get better” isn’t testable. “My sales will increase by 10% this quarter” is testable.

The vaguer your guess, the easier it is to claim you were right no matter what happens. This is how psychics stay in business. Don’t trick yourself the same way.

Moving the Goalposts

You predicted X. X didn’t happen. Now you say, “Well, what I really meant was Y.”

If you catch yourself changing what “success” means after you see what happened, you’re not testing - you’re making excuses. Lock in your guess before you see the results, or the whole exercise is useless.

Cherry-Picking

You remember the times you were right. You conveniently forget the times you were wrong.

This is why you need to write things down. Your memory can’t be trusted here - it works for your ego, not for the truth.

The Unfalsifiable Belief

“Everything happens for a reason.” “The universe is testing me.” “They secretly agree with me but can’t admit it.”

These beliefs explain everything, which means they explain nothing. If a belief fits with any outcome - if nothing could ever prove it wrong - then it’s not connected to reality. It’s just a story you tell yourself. You can’t test it because nothing can prove it false.

When Testing Is Hard

Some beliefs are genuinely hard to test directly:

  • Historical claims (you can’t run experiments on the past)
  • Rare events (not enough data points for statistical confidence)
  • Complex systems (too many variables to isolate)

For these, you need proxies:

  • Expert consensus - What do people who study this full-time believe? Not one expert with a book to sell-the aggregate view of people with relevant expertise.
  • Track records - Have similar predictions been accurate in the past? If someone’s been consistently wrong, that’s data.
  • Alternative explanations - What else could explain the evidence? Have you seriously considered competing hypotheses?

The Emotional Part

The hardest part of testing beliefs isn’t thinking - it’s feeling.

Finding out you’re wrong feels bad. Your sense of who you are might be tied up in certain beliefs. Admitting you were wrong can feel like admitting you’re weak - especially when people around you act like changing your mind is a flaw.

But think about it: Changing your mind when the facts say you should is a sign of strength, not weakness. It takes guts to update your beliefs. Most people never do. They just defend what they already think, forever, no matter what.

The goal isn’t to always be right - that’s not possible for humans. The goal is to be less wrong over time. Every belief you fix is a step forward.

Practical Steps

  1. Pick one belief that affects your daily life
  2. Ask what you’d expect to see if it were wrong
  3. Look for that evidence deliberately
  4. Write down what you find (not what you remember-what you write down)
  5. Update your belief accordingly (or don’t, if the evidence supports it)

Start small. Test one assumption this week. See what happens when you actually look for disconfirming evidence instead of just passively believing what you’ve always believed.

What’s Next

Part 2 covers the either/or trap-the tendency to see only two options when reality usually offers more. This binary thinking is one of the most common ways our reasoning goes wrong, and you probably do it more than you realize.

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