This document discusses the "Hedgehog Concept" of simplicity within three intersecting circles. It describes how hedgehogs focus on a single, core idea to simplify complex problems, unlike foxes which pursue many ideas. Examples are given of individuals like Darwin who had a unified concept. The concept is then related to businesses like Walgreens that achieved success with a simple drugstore model, unlike imitators like Eckerd. The document concludes by defining the three intersecting circles of the Hedgehog Concept as what you are best at, what drives your economic engine, and what you are deeply passionate about.