  Hermann Weyl was a great and versatile mathematician of the  20th century. His work had a vast range, encompassing  analysis, algebra, number theory, topology, differential geometry,  spacetime theory, quantum mechanics, and the foundations of  mathematics. His scientific writing is informed by a rare literary  and artistic sensibility—in his words, “Expression and  shape mean almost more to me than knowledge itself”. He was  unusual among scientists and mathematicians of his time in being  attracted to idealist philosophy: his idealist leanings can be seen  particularly in his work on the foundations of mathematics. In his  youth, Kant’s doctrines made a great impression on him; later he was  stirred both by Fichte’s metaphysical idealism and by Husserlian  phenomenology. Although Weyl came to question the certainties claimed by idealism, he cleaved always to the primacy of intuition he had  first learned from Kant, and to its expression by Fichte as the  “inner light” of individual consciousness.