This book uses Ludwig Wittgensteins philosophical methodology to solve a problem that has perplexed thinkers for thousands of years: 'how come (abstract) mathematics applies so wonderfully well to the (concrete, physical) world?'The book is distinctive in several ways. First, it gives the reader a route into understanding important features of Wittgensteins writings and lectures by using his methodology to tackle this long-standing and seemingly intractable philosophical problem. More than this, though, it offers an outline of important (sometimes little-known) aspects of the development of mathematical thought through the ages, and an engagement of Wittgensteins philosophy with this and with contemporary philosophy of mathematics on its own terms. A clear overview of all this in the context of Wittgensteins philosophy of mathematicsis interesting in its own right; it is also just what is needed to solve the problem of mathematics and world.