Teach It Back

Feynman's insight was deceptively simple: try to explain something in plain language, and where you get stuck — where you resort to jargon, where you wave your hands, where you say "it basically just works" — those are the gaps. The Feynman Technique as usually practised has a limitation though: you're explaining to a wall. There's no one to catch your subtle errors, your circular reasoning, or your confident misstatements. This skill is the wall that talks back.

The listening is structured. While you explain, the skill tracks specific patterns. Jargon without definition — using a technical term you can't unpack. Confidence changes — where the explanation speeds up (comfortable territory) versus slows down (the boundary of your real understanding). Vague connectives — "it basically...", "it kind of...", "it just..." — these signal hand-waving over a mechanism you don't fully understand. Circular explanations — defining X in terms of Y, then Y in terms of X. Confident errors — the most dangerous category, because you don't know you're wrong.

What follows the explanation isn't a quiz; it's a clarification round, then a stress test. Edge cases ("you explained how this works in the normal case — what happens when this unusual condition holds?"). Counterexamples ("you said this is generally true — what about this scenario that seems to contradict it?"). Analogy probes ("you used the phone-book analogy — where does it break down?"). Depth probes ("you explained the what — why does it work that way?"). Each question targets a specific kind of gap, and the gap that survives multiple angles is the one worth fixing.

The output is a Gap Map with four categories. What you truly understand — concepts you explained clearly and defended under questioning. Partial understanding — you have the shape but not the mechanism. What you think you understand but don't — the dangerous category of confident misconceptions. What you know you don't know — honest ignorance, which is easy to fix because it just requires study.

When you got something wrong, the skill guides you to the correction through questions rather than lecturing — because the self-discovered gap sticks and the told gap bounces. When Socratic guidance stalls (you're missing a prerequisite, not failing the test), the skill stops and teaches directly, then asks you to re-explain integrating the correction. When your explanation was genuinely good, the skill says so and probes one edge case to find the boundary of your understanding rather than manufacturing problems that don't exist.