Find the Root
Your kitchen sink keeps clogging. You snake it. Two months later it clogs again. You buy a stronger snake. Three months later, the same thing. The drain isn't the problem. The grease trap was never installed.
Most people stop one "why" too early. They land on a contributing factor and call it a cause. The hire who left. The vendor who missed. The launch that flopped. Each is true. None is bedrock.
First principles is the discipline of refusing inherited answers. The five whys aren't a ritual, they're a stress test. You ask why until the answer stops describing this situation and starts describing how the system works. "I'm late because I had back-to-backs" is the same shape as "I'm late." Both describe the event. "I book my calendar without buffer" describes the system. Different category. That's where the fix lives.
You know you've reached the root when the fix feels small and slightly uncomfortable. Small because you're not adding new process, you're removing what was generating the problem. Uncomfortable because root causes usually point at a default you've been protecting: a hire you didn't want to make, a meeting you didn't want to cancel, a yes you didn't want to take back.
Try it on a recurring fight at home. The kid won't go to bed. New bedtime routine. New app. New rules. Then you notice the kid naps every afternoon because it's easier on you. The bedtime fight isn't a bedtime problem. It's an afternoon problem. The fix is small. Skipping the nap is uncomfortable for a week.
This compounds quietly. The person who keeps digging stops getting hit by the same problem in new costumes. Their team notices. Their decisions age well. They look slow in the moment and fast over a year.
Symptoms beg for activity. Causes ask for honesty. Stay with the question until the answer changes category.