For curious nonmathematicians and armchair algebra buffs, John Derbyshire discovers the story behind the formulae, roots, and radicals. As he did so masterfully in Prime Obsession , Derbyshire brings the evolution of mathematical thinking to dramatic life by focusing on the key historical players. Unknown Quantity begins in the time of Abraham and Isaac and moves from Abel’s proof to the higher levels of abstraction developed by Galois through modern-day advances. Derbyshire explains how a simple turn of thought from "this plus this equals this" to "this plus what equals this?" gave birth to a whole new way of perceiving the world. With a historian’s narrative authority and a beloved teacher’s clarity and passion, Derbyshire leads readers on an intellectually satisfying and pleasantly challenging journey through the development of abstract mathematical thought.

John Derbyshire知名科普作家，数学家，教育语言学家，专业系统分析师。除本书外，他还著有广受好评的Pr／me Obsession和Seeing Calvin Dream。他的作品经常刊登在美国《国家评论》和《新标准》等杂志上。