D O C U M E N T 2 3 J U LY 1 9 2 7 4 3 Wittgenstein, who has written a Tractatus logico-philosophicus (published by Bertrand Russell in English and in German) that I consider the deepest and truest book of modern philosophy in general.[3] However, it is extremely difficult to read. The author, who has no intention of ever writing anything further, has an artistic nature of captivating brilliance, and discussion with him is one of the most power- ful intellectual experiences of my life. His basic insight seems to me to playfully overcome the difficulties of Russell’s system, and in principle the whole founda- tional crisis of contemporary mathematics as well.[4] I believe I have learned a great deal and can hardly say how primitive and immature my theory of knowledge now appears to me.[5] Please forgive me if I tell you these things, because you are probably concerned with quite different problems. But what fills the heart runs over into the mouth, and since I recall that two years ago you were interested in Russell’s mathematical philosophy, and [since] I don’t know whether you have already somehow become acquainted with Wittgenstein’s logic, I have taken the liberty of referring to it as something truly great and deep. Perhaps in your leisure hours you might like to explore this area, where (in contrast to physics) we find no genuine expansion of knowledge, but instead intellectual reassurance. With best wishes for your good health and work, gratefully and sincerely yours, M. Schlick 23. To Elsa Einstein [Leukerbad, 16 July 1927] Dear Elsa, So I’m sitting here in Leukerbad, and the sessions in Geneva start again on the 20th.[1] It is, one might say, beautiful here, a high valley, 1400 meters. In the little train I took to get here I met Wolf from the Berl.[iner] Tageblatt and his son.[2] The air is good, but I don’t like living in the hotel. I can’t imagine sitting around here with Tete for two weeks.[3] It would be so much nicer to be in Berlin and go sailing. But I don’t know whether I can persuade Tete to do that for a short time. In any case, I’m still not sure what will happen. You would probably like the whole thing better. All the mischief comes from the damned League of Nations. But I can hardly get away decently. Best regards to you, Ilse, and Rudi[4] from your Albert I’ve written to the Argentinians.[5] Have you sent the Swiss passport to Thayngen?