This volume takes Hermann Weyl's "Raum - Zeit - Materie" (Space - Time - Matter) as a centre of concentration and a starting field for a broader look at his work. The book looks at Weyl's involvement in relativity, cosmology and matter theories between the classical unified field theories and quantum physics from the perspective of a creative mind struggling against theories of nature restricted by the view of classical determination. It also covers Weyl's work in the mathematical sciences in general and in philosophy. The range covered includes: real analysis; complex function theory and Riemann surfaces; elementary ergodic theory; foundations of mathematics; differential geometry; general relativity; Lie groups; quantum mechanics; and number theory.