  Weyl’s book, Raum-Zeit-Materie, beautifully exemplifies the  fruitful and harmonious interplay of mathematics, physics and  philosophy. Here Weyl aims at a mathematical and philosophical  elucidation of the problem of space and time in general. In the  preface to the great classical work of 1923, the fifth German  edition, after mentioning the importance of mathematics to his work,  Weyl says: 