 From 1913 on, Brouwer increasingly dedicated himself to the development of the ideas formulated in his dissertation into a full philosophy of mathematics. He not only refined the philosophy of intuitionism but also reworked mathematics, especially the theory of the continuum and the theory of sets, according to these principles. By then, Brouwer was a famous mathematician who gave influential lectures on intuitionism at the scientific meccas of that time, Cambridge, Vienna, and Göttingen among them. His philosophy was considered awkward by many, but treated as a serious alternative to classical reasoning by some of the most famous mathematicians of his time, even when they had a different view on the matter. Kurt Gödel, who was a Platonist all his life, was one of them. Hermann Weyl at one point wrote “So gebe ich also jetzt meinen eigenen Versuch Preis und schließe mich Brouwer an” (Weyl 1921, 56). And although he rarely practised intuitionistic mathematics later in life, Weyl never stopped admiring Brouwer and his intuitionistic philosophy of mathematics.