5.2 The structures of propositions stand to one another in internal relations.
A winter evening in 1927, Professor Maurice Schlick comes to dinner at Gretl Wittgenstein's home to make the long delayed meeting of Ludwig Wittgenstein. Mrs Schlick: "I observed with interest the reverential attitude of the pilgrim." Ludwig: "Each of us thought the other must be mad."

By degrees Schlick coaxes the prickly philosopher to attend Monday discussions with himself, Rudolf Carnap, Friedrich Waismann, Herbert Feigl. But Wittgenstein often will not discuss the positivist philosophical ideas the others espouse. He turns his back on them and reads poetry.

Carnap: "His point of view toward people and problems was much more similar to a creative artist than a scientist. When finally, sometimes after a prolonged arduous effort, his answer came forth, his statement stood before us like a newly created piece of art or a divine revelation."

March 1928, Wittgenstein attends a lecture by the intuitionist mathematician L.E.J. Brouwer. Brouwer the antirationalist claims mathematics is only a construction of the human mind, that theorems which cannot be proved must be cast aside.

Wittgenstein is transformed. Feigl: "He became extremely voluble and began sketching ideas that were the beginnings of his later writings. That evening marked the return of Wittgenstein to strong philosophical interest and activities."