This book tackles the important questions which have engaged mathematicians, scientists, and philosophers for thousands of years and which are still being asked today. It does so with clarity and with scholarship born of first-hand experience; a knowledge both of the ideas and of the people who have pronounced on them. The main purpose of the book is to confront philosophical problems: In what sense do mathematical objects exist? How can we have knowledge of them? Why do mathematicians think mathematical entities exist for ever, independent of human action and knowledge? The book proposes an unconventional answer: mathematics has existence or reality only as part of human culture. Despite its seeming timelessness and infallibility, it is a social, cultural, historic phenomenon.