The Feynman Technique: If You Can't Explain It Simply, You Don't Understand It

The Feynman Technique is a way to test whether you actually understand something, rather than just recognise it. You try to explain the idea in plain language, out loud or on paper, and you watch for the exact moment the explanation breaks down. That moment is the useful part.

The method is usually written as four steps: pick an idea, explain it simply, find where the explanation falls apart, then go back to the source and close the gap. It's named after the physicist Richard Feynman — though, as with a lot of famous frameworks, the tidy version came later.

1. Feynman never named the "Feynman Technique." The four-step method was formalised by later writers — the popular version is often credited to Scott Young. Feynman's real contribution was how he actually learned and taught: relentlessly, in plain language, from first principles.

2. The core idea comes from a real admission. His colleague David Goodstein once asked Feynman to explain why a certain class of particles obeys a particular rule. Feynman offered to prepare a freshman lecture on it, then came back a few days later and said: "I couldn't reduce it to the freshman level. That means we don't really understand it."

3. Step one is to explain it to a beginner. No jargon, no shorthand — plain words, and where you can, an everyday analogy. The audience in your head should be a curious twelve-year-old, not a colleague who already shares your vocabulary.

4. The stumble is the signal. The moment you reach for a technical term to paper over a gap, you've found the edge of what you actually know. Mark it, return to the source material, and fill it in — then try the explanation again.

5. Jargon is where fake understanding hides. Feynman liked to point out that knowing the name of something isn't the same as knowing it — you can say "the half-life is exponential" and understand none of it. Plain language removes that hiding place, because there's nothing left to hide behind.

6. The last step is to simplify and refine. Rewrite until the explanation runs without a pause. If it now reads cleanly to someone outside the field, you understand it. If it still needs the reader to already know the field, you don't — yet.

The technique's real value isn't the teaching; it's the honesty it forces. Re-reading a chapter feels like learning because it's smooth and familiar. Explaining is bumpy — and the bumps are a fairly accurate map of everything you don't yet know.