If you are reading this, you are a chronic concept-user. You have at your disposal a staggering repertoire of concepts, which you use round the clock to great effect. Many of these concepts correspond to mundane categories such as doorknob, Tuesday and pigeon. Other of your concepts are so entangled with things that matter to you that mere mention of them may trigger a cascade of associations and emotions. Consider: Grief. Intimacy. Betrayal. Compassion. Genocide. The concepts you possess are not inert objects that sit like ornaments on some shelf in your mind. They are the very tools which you use to plan; think through problems; navigate and interact with a world of familiar objects, people and events; and to understand and formulate sentences. The measure of good politics, good science, good poetry and, of course, good philosophy, is very often the skilful use of concepts.