Why does idea decomposition fail?

The most common reason idea decomposition fails: Stopping at the first level of decomposition and calling it done. You break 'launch the product' into five steps and feel satisfied — but each of those five steps contains its own hidden complexity. The illusion of explanatory depth operates at every level, not just the top. If you haven't hit a point where you're uncertain, you haven't decomposed far enough.

The fix: Pick one thing you believe you understand well — a process at work, a technology you use daily, a decision you recently made. Set a 10-minute timer and write a step-by-step decomposition: break it into every sub-part, dependency, and assumption you can identify. When you hit a step you cannot explain clearly, mark it with a question mark. Count the question marks. That number is the gap between your felt understanding and your actual understanding.

The underlying principle is straightforward: You do not understand something until you can decompose it — and the act of decomposition will show you exactly where your understanding breaks down.