Bertrand Russell 
Introduction to Mathematical Philosophy 

Brilliant introduction to the philosophy of mathematics, from the question ‘what is a number?’ up to the concept of infinity, descriptions, classes and axioms Russell deploys all his skills and brilliant prose to write an introductory book — a real gem by one of the 20th century’s most celebrated philosophers New foreword by Michael Potter to the Routledge Classics edition places the book in helpful context and explains why it’s a classic