## ABSTRACT

Once, in his later years, Cornelius Lanczos was asked what above all he would like to be remembered for. His answer, given in Rodin’s article in Further Reading, was clear and deﬁnite: ‘‘For having introduced a new style of text book’’. His answer may have been surprising because one might have expected him to have chosen some of his well-known and widely-used methods in applied mathematics, or one of his many papers on the theory of relativity, quantum mechanics or electromagnetism. In this new style of textbook, he put the emphasis on ideas and concepts and their mutual interrelation, rather than on the mere manipulation of formulae.