This catalogue of the world's most influential philosophers begins with Pythagoras. Best known today as a mathematician, Pythagoras claimed that numbers underpin the harmonious structure of the world. He developed a set of principles that guided his fellow Greek philosophers Plato and Aristotle, among others. The volume ends with the contributions of the Indian Buddhist philosopher Nagarjuna, who expanded the idea of the "middle way" between the extremes of existence and nonexistence. Detailed biographies of these philosophers--as well as Confucius, Socrates, Zhuangzi, and others--introduce readers to the early discipline of philosophy and its enduring ideas.