Knowing What You Don't Know

The most valuable part of the circle of competence is defining its boundary — knowing where your genuine knowledge ends and your guessing begins. Inside the circle, trust your judgment. On the boundary, proceed carefully and seek expert input.

You can catch yourself at the edge of your competence by one telling symptom: you are defending a position you have never actually tested. The opinion feels solid, but it rests on borrowed confidence rather than direct experience.