While the published works of Ludwig Wittgenstein reveal the final, coalesced thoughts of this philosophical giant, Wittgenstein's diary reveals his process of doing philosophy. Only in his private writing does Wittgenstein's philosophical practice fully come to light. Wittgenstein's diary entries from the 1930s reveal themselves as a first-person spiritual epic. Wittgenstein agonizes over his relationship with Marguerite Respinger and tries to come to terms with its failure. He relates and interprets several of his dreams. He comments on his philosophical colleagues Frank Ramsey and G.E. Moore; on musicians such as Beethoven, Bruckner and Brahms; and on authors such as Kraus, Mann, Nietzsche, Dostoevsky, and Kierkegaard. He struggles to make confessions to friends and family. He relates in painful detail his spiritual crisis in Norway in the late winter of 1937. From a man who once recommended silence about spiritual matters, we find here an honest and searing articulation of his attempts to believe and live what he finds in the Bible. Here are the raw materials for what could have been one of the great spiritual autobiographies of the twentieth century. It is available here for the first time in an affordable edition, with updated and expanded editorial notes to help the reader understand Wittgenstein's many allusions, and with a new Introduction by Ray Monk, which places the diary in the larger arc of Wittgenstein's life.