People are fascinated by the hidden lives of creative geniuses, the more sordid the better. Wittgenstein’s Private Notebooks, 1914-1916 appeals to that interest by allowing the reader to eavesdrop on his agonised emotional life in two of those years of military service, during which he produced one of the most influential philosophical works of the 20th century. The Tractatusis a founding document of the analytic tradition in philosophy. It set out a theory of logic, language and the limits of meaning which revealed, Wittgenstein argued, that traditional philosophical problems were based on linguistic confusion. The two tracks of his life – the emotional and the intellectual – can be followed in some notebooks Wittgenstein kept during that period. On the right-hand pages he entered his philosophical thoughts, in legible German. On the left-hand pages, in code, he entered his personal feelings – hopes, fears, prayers, despair, loathing of himself and other people, and gratitude when he was able to work.