In the mid-1930s, when the eminent Jewish historian Simon Dubnow began to publish his autobiography, he gave it the formidable title The Book of Life: Reminiscences and Reflections, Material for the History of My Time. Drawing not only on his memory, but on copious diaries and a prodigious literary output going back to the 1880s, Dubnow traced his journey from shtetl Judaism to Jewish nationalism—a journey typical (onemight almost say prototypical) of the late-nineteenth-century Russian Jewish intellectual's search for a new definition of himself as Jew and modern man. The substance of Dubnow's Book of Life frees the title from pretentiousness; more than a mere compilation, much of the autobiography (especially the first volume and a half) was an act of synthesis and integratsiia dushi (“self-integration”), two of Dubnow's favorite terms. My aim in this paper is to reflect anew on the process of Dubnow's self-integration, bridging the gap between a purely biographical approach and a purely ideological one in order to show how a distinctive nationalist stance crystallized out of Dubnow's personal growth. Nationalism was a hard-won, by no means self-evident solution to an overlapping sequence of emotional and intellectual dilemmas. Dubnow provides us with a picture of the groping that this self-transformation entailed, a picture that can be supplemented, and to a certain extent revised, by listening for resonances between life and thought undetected by Dubnow himself.