How Toyota debugs reality.
A machine stops. Most people fix what they see and move on. Toyota engineers ask why five times:
1. Why did it stop? The fuse blew. 2. Why? The bearing seized. 3. Why? No lubrication. 4. Why? The pump wasn't working. 5. Why? The pump's shaft was worn from metal shavings getting in.
Fix the fuse, it breaks again next week. Fix the shavings problem, it never happens again.
Most failures you face aren't the real problem — they're the symptom standing where the problem should be. The first answer is almost never the root. Keep asking why until the cause can't hide behind another cause.