# How to Write to Teach **A guide to explanatory writing for Brainfolds** --- Read a textbook definition of photosynthesis. Now read the opening of chapter 8 in Botany Basics. One gives you a fact to memorise. The other makes you want the fact before it gives it to you. That difference — between writing that puts the definition first and writing that puts the problem first — is what every chapter in Brainfolds is built on. ## The core principle The reader must feel why something matters before they are asked to learn what it is. Most educational writing fails because it starts with the definition. Students read definitions, recognise them as things to memorise, and forget them within a day. Good explanations start with a problem, a surprise, or a consequence — something that makes the reader want the definition before you give it to them. --- ## Rule 1 — Answer "why does this exist" before "what is it" Every concept was invented to solve a problem. Find that problem and put it first. The definition should arrive as the answer to a question the reader is already asking. **✗ Bad:** "The Casparian strip is a band of suberin in the endodermis of plant roots that prevents apoplastic flow of water and solutes." **✓ Good:** "Plants have a serious security problem: they need to absorb water and minerals from the soil, but they can't afford to let everything in indiscriminately. The Casparian strip is the solution: a watertight seal built into the root's inner wall that forces everything through a living cell checkpoint." --- ## Rule 2 — Anchor every technical term to something the reader already knows The first time you use a technical term, tie it to something concrete and familiar. The reader should feel that they already half-knew this word, they just didn't have it yet. Test your analogy: push it one step further. If it breaks immediately, it is misleading, not clarifying. **✗ Bad:** "Cellulose microfibrils form the structural component of the primary cell wall." **✓ Good:** "Cellulose microfibrils — the same material as cotton thread and paper — are woven into a mesh that forms the primary cell wall. Every piece of wood you have ever touched is mostly cell wall." --- ## Rule 3 — Give the practical consequence — what breaks when this fails Theory becomes real when you show what happens when the system fails. Every section should have a direct path to something observable, diagnosable, or avoidable in practice. **✗ Bad:** "Turgor pressure maintains cell rigidity in plant tissue." **✓ Good:** "Turgor pressure is what makes a lettuce leaf crisp. When a cell fills with water it pushes outward against the rigid cell wall — that pressure is the crispness. When the plant can't replace water fast enough, pressure drops, cells go slack, and the plant wilts." --- ## Rule 4 — Identify the two or three things that actually matter Every major section should have a moment where the reader knows what is essential versus what is supporting detail. State it explicitly — "Two things to hold onto:" or "The one thing that matters here is..." If you can't identify the most important things in a section, it probably covers too much, or you don't yet understand the material well enough to teach it. --- ## Rule 5 — Use the specific, not the generic The strongest teaching examples are ones the reader can walk outside and observe, touch, or do today. Generic illustrations give the reader nothing to grip. Specificity is not decoration. It is what makes the concept stick. **✗ Bad:** "Some soils have high clay content which can affect drainage and workability." **✓ Good:** "The Blackland Prairie — the dark, sticky clay belt running from San Antonio northeast to Dallas — shrinks and cracks in summer drought and swells when wet enough to heave fence posts out of the ground." --- ## Rule 6 — End every section with what this unlocks The last sentence or two of every major section should tell the student what they can now understand or do that they couldn't before. This makes the curriculum feel like a sequence rather than a collection of isolated facts. --- ## Rule 7 — Order by dependency, not by importance Sequence ideas by what the reader needs to understand before the next idea makes sense. The practical sequence that works for most sections: 1. **The problem or gap** — something is broken, surprising, or unexplained 2. **The stakes** — why does this problem matter? 3. **The concept, named** — now you earn the definition 4. **The mechanism** — how does it actually work? 5. **The failure mode** — what breaks when it fails? 6. **What it unlocks** — where does this connect forward? **Concrete before abstract, always.** If you're going to make a general claim, make the specific case first and let the reader abstract upward. --- ## Rule 8 — Cut before you publish Every concept you add costs the reader attention they could spend on something load-bearing. The question is not "is this interesting?" — the question is "does the reader need this to understand what comes next?" Three cuts worth making deliberately: - Cut the caveat that doesn't change the conclusion - Cut the history that doesn't explain the present - Cut the synonym list --- ## Rule 9 — End sections with a question the reader can now answer After applying Rule 6, add one real-world question the student can now answer that they couldn't before the section. Not a quiz question. A question that would occur to a curious person encountering this concept in practice. --- ## The Before/After Test Before publishing any section, ask: 1. Would a curious 14-year-old understand the first sentence without a dictionary? 2. Is there at least one thing they can go outside and observe, test, or do today? 3. If they forget everything except one sentence, which sentence would you want it to be — and is that sentence actually in there? --- *The enemy is not complexity. The enemy is writing that treats the reader as a container to be filled with facts rather than a person trying to understand something real.*