Explaining a Hard Idea: Why Knowing It Makes You Worse at Teaching It

The people best at a subject are often the worst at explaining it — not from arrogance, but because expertise erases the memory of not understanding.

You no longer notice the steps you skip, because to you they are not steps.

The gap you cannot see

• You compress several steps into one without noticing.
• You use terms that feel plain to you and are not.
• You start from the structure of the subject, not from where the learner is.
• You skip the part you personally found obvious — which is often the part others find hardest.

The fix is not to simplify. It is to find out where the learner actually is, and build from there.

Build from what they already know

• Ask what they already understand about the area before explaining anything.
• Connect the new idea to something familiar — this is what makes an explanation stick.
• Name the misconception if there is a common one. People cannot absorb a correct model while holding an incorrect one; the wrong idea has to be addressed directly.
• Go one step at a time and check before moving on.

Using examples properly

• Concrete before abstract. Show a specific case first, then generalise. Almost every confusing explanation does this in the opposite order.
• Use more than one example — a single example gets learned as the rule.
• Include a non-example — showing what the concept is not sharpens the boundary faster than more examples of what it is.
• Choose examples from their world, not yours.

Analogies: useful and dangerous

• A good analogy makes an idea graspable immediately.
• Every analogy breaks somewhere — and learners will follow it past that point.
• So state where it breaks, explicitly. This one habit prevents a lot of later confusion.
• Drop the analogy once it has done its job — do not build further ideas on top of it.

Checking understanding

Asking whether that makes sense does not work. People say yes for social reasons and because they do not yet know what they have missed.

What works:

• Ask them to explain it back in their own words.
• Give a new case and ask them to apply it.
• Ask what would happen if — a question that requires the model, not the words.
• Ask what part is still unclear — this gets better answers than asking if anything is unclear, because it assumes something is.

When someone is stuck

• Do not repeat the same explanation louder. If it did not work the first time, it will not work the third.
• Find out what they think is happening — the wrong model tells you exactly which explanation is needed.
• Go back further than feels necessary. The block is usually earlier than where it surfaced.
• Try a different mode — draw it, walk through a concrete case, have them do it while you watch.
• Give it time. Some ideas need a night in between; pushing harder in the moment rarely helps.

Language

• Define a term the first time you use it, then use it consistently.
• Do not use two words for the same thing — learners assume they are different.
• Prefer short sentences. Complexity of subject does not require complexity of sentence.
• Watch for words with a specialist meaning that differs from ordinary use — these are a major source of silent misunderstanding.
• For learners working in a second language, plain language and consistent terms matter even more.

Structure of a good explanation

• Say what it is for before saying what it is. People retain explanations better when they know why they need them.
• Give the short version first, then the detail. Detail without a frame is hard to hold.
• Show a worked example all the way through.
• Have them do one while you watch.
• Summarise in one sentence at the end.

Getting better at this

• Notice the questions you get repeatedly — each one marks a place your explanation fails.
• Keep a note of the misconceptions you encounter; they are the most valuable teaching material you own.
• Watch someone else teach the same thing.
• Ask a beginner to explain it back and listen for the distortion — that is where your version was ambiguous.

One thing worth remembering

The mark of a good explanation is not that it sounds thorough. It is that the learner can use the idea afterwards without you present.

Everything above is a way of testing for that earlier rather than later.

FAQ