The four steps
The whole method fits in four moves:
- Pick a concept you want to understand and write it at the top of a page.
- Explain it in plain language, as if teaching a curious 12-year-old — no jargon.
- Notice where you stall, hand-wave, or fall back on borrowed terms. Those are your gaps.
- Go back to the source, fill the gap, and re-explain until it flows.
Why explaining reveals what you don't know
Reading and nodding along creates an illusion of understanding — the words are familiar, so you assume the meaning is too. Explaining breaks the illusion. The moment you have to produce the idea in your own words, every fuzzy spot becomes obvious.
It's active recall aimed at understanding rather than facts: instead of "what's the answer," it asks "can I actually reconstruct this from scratch?"
Combine it with flashcards
The Feynman technique is how you find weak spots; flashcards are how you keep the fixes from fading. When an explanation exposes a gap, make a card (or a few) for the specific facts or reasoning you missed, and let spaced repetition keep them fresh.
Together they cover both halves of real learning: genuine understanding, then durable retention.