This paper attempts to summarise the philosophical career of Bertrand Russell, concentrating in particular on his contributions to logic and the philosophy of mathematics. It takes as its starting point Russell's conception of philosophy as the search for foundations upon which certain knowledge might be built, a search which Russell, at the end of his career, declared to be fruitless. In pursuing this search, however, Russell was led to develop lines of thought and techniques of analysis that have had a profound and lasting influence on the philosophy of the twentieth century.