Bertrand Russell is the most important philosopher of mathematics of the twentieth century. The author of The Principles of Mathematics and, with Alfred Whitehead, the massive Principia Mathematica , Russell brought together his formidable knowledge of the subject and his skills as a gifted communicator to provide a classic introduction to the philosophy of mathematics. Introduction to Mathematical Philosophy sets out in a lucid and non-technical way the main ideas of Principia Mathematica . It is as inspiring and useful to the beginner now as it was when it was first published in 1919. This paperback edition of Introduction to Mathematical Philosophy includes a new introduction by John G. Slater, University of Toronto.