The philosopher Isaiah Berlin wrote an essay dividing the world into foxes and hedgehogs. Foxes know many things. Hedgehogs know one big thing. Collins uses this distinction as a metaphor for organisational focus. Good-to-great companies were not necessarily better at more things than their competitors. What made them great was that they found the one thing they could be genuinely the best at, and then pursued it with relentless focus. The Hedgehog Concept sits at the intersection of three circles. First: what can you be the best in the world at? Not the best at many things, and not the best in your industry, but genuinely world-class at one specific thing. Second: what drives your economic engine? What single metric, if optimised, would most directly drive sustainable profitability? Third: what are you deeply passionate about? Not what you can force yourself to be interested in, but what genuinely energises you. Where all three circles overlap is the Hedgehog Concept. For great companies, strategy became ruthlessly simple: do more of what sits inside the circles, and stop doing everything else. Most organisations pursue many things at varying levels of competence. They spread effort across too many areas and become mediocre at all of them. The discipline of the Hedgehog is the discipline of stopping: saying no to opportunities, customers, and expansions that fall outside the intersection, no matter how attractive they look.