Wittgenstein and Cambridge Family Resemblances

Russell to Ottoline Morell,
18 October 1911
He turned out to be a man who had learned engineering at Charlottenburg, but during his course
had acquired, by himself, a passion for the philosophy of math’s, and has now come to Cambridge
on purpose to hear me.
19 October 1911
My German friend threatens to be an infliction, he came back with me after my lecture and argued
till dinner-time – obstinate and perverse, but I think not stupid.
1 November 1911
My German engineer very argumentative and tiresome.
2 November 1911
My German engineer, I think is a fool. He thinks nothing empirical is knowable – I asked him to
admit that there was not a rhinoceros in the room, but he wouldn’t.
13 November 1911
[M]y German ex-engineer, as usual, maintained his thesis that there is nothing in the world except
asserted propositions, but at last I told him it was too large a theme […]
16 November 1911
My ferocious German came and argued at me after my lecture, […] He is armour-plated against all
assaults of reasoning – it is really rather a waste of time talking with him.
27 November 1911
My German is hesitating between philosophy and aviation; he asked me today whether I thought he
was utterly hopeless at philosophy, and I told him I didn’t know but I thought not.
29 November 1911
I am getting to like him, he is literary, very musical, pleasant-mannered (being an Austrian) and I
think really intelligent.
Russell in his Autobiography, 1959
He was perhaps the most perfect example I have ever known of genius as traditionally conceived,
passionate, profound, intense, and dominating.
Wittgenstein to Russell, Skjolden,
29 October 1913
Identity is the very Devil and immensely important; very much more so than I thought. It hangs – like
everything else – directly together with the most fundamental questions, especially with the questions
concerning the occurrence of the same argument in different places of a function. I have all sorts of
ideas for a solution of the problem but could not yet arrive at anything definite. However I don’t lose
courage and go on thinking. –
November 1913
Lieber Russell!
I intended to write this letter in German, but it struck me that I did not know whether to call you
„Sie“ or „Du“ so I am reduced to my beastly English jargon! –
In his answer Russell offered Wittgenstein to call him „Du“. The following letter Wittgenstein wrote
already in German, Russell answered as always in English. This continued until Wittgenstein was taken
prisoner in Italy after the Great War. From there he wrote in English, as well as his last two letters to
Russell from 1935.