Understanding often feels real right up until the moment you try to explain it.

If you can’t explain something in your own words, you probably don’t understand it yet.

You might recognize the terms. You might nod along. But that’s not understanding that’s familiarity pretending to be knowledge.

One of the fastest ways to puncture that illusion is to think out loud. Write the idea as if you’re explaining it to a curious beginner. No jargon. No shortcuts. Just plain language. The moment you try this, the fog shows up exactly where your understanding is weak.

You can go even further by teaching the idea—to a friend, a colleague, or an invisible audience on the internet. As Feynman believed, teaching isn’t a byproduct of understanding; it’s the stress test.

When you get stuck mid-explanation, that’s not failure. That’s the location of learning.