 On March 10, 1928, Brouwer lectured in Vienna on his intuitionistic foundations of mathematics. Ludwig Wittgenstein attended that lecture, persuaded by Herbert Feigl, who afterwards wrote about the hours he spent with Wittgenstein and others after the lecture: a great event took place. Suddenly and very volubly Wittgenstein began talking philosophy – at great length. Perhaps this was the turning point, for ever since that time, 1929, when he moved to Cambridge University, Wittgenstein was a philosopher again, and began to exert a tremendous influence.