8 0 D O C U M E N T 7 5 O C T O B E R 1 9 2 7 the most distinguished hotel in Brussels, right across from the castle.[4] It might just as well be in Mecklenburg-Strelitz.[5] People must go there to rest up. Even the ho- tel staff is rustically ingenuous, and the cab driver tries to cheat you, but in an up- rightly clumsy way. I was left in peace all day and no one knows about my existence in this place. That makes one notice for the first time what a mad rush we normally live in. When people speak in this city’s academy, they get a kind of goose-bumps.[6] But it’s harmless. In the afternoon, a walk to the cathedral and the main city square, in very cold weather.[7] It’s really splendid. Flemish art is so cheerful. Then I slept in my room until 5:30, and now I’m dining in the hotel. At the moment I’m trying to wipe the grease off my lips. 75. From and to Paul Ehrenfest [Brussels,] Tuesday morning (Compton II) [25 October 1927][1] Don’t laugh![2] There’s a special department in purgatory for “professors of quantum theory,” and there you will receive, for ten hours a day, lectures on classical physics.[3] I’m only laughing at the naïveté. Who knows who’ll be laughing in a few years?[4]