"Monday mg." Wittgenstein "was explaining a number of very difficult logical ideas which I could only just understand by stretching my mind to the utmost. He was certainly the chief cause of my fatigue before. I feel him so terribly important and precarious that I go on making efforts when I should have given up with anybody else. For my own sake (and for yours) it is a godsend his going to Norway. It turns out that he can come back at any time to finish the residence for a degree and he says he means to come back when he has got something written. He has promised to leave me a written statement of what he has already done before he starts for Norway. The more he talks about it, the more admirable I think it. He is certainly quite supreme. He and Whitehead and I are all in a fruitful vein, so I feel very happy about work."