Sabath on Kaplan Diaries/p. 1 The Private Evolution of Kaplan’s Radical Religious Hope: The Three Volumes of Communings of the Spirit Rachel Sabath Beit-Halachmi Reviewing Communings of the Spirit: The Journals of Mordecai M. Kaplan, 3 vols. Edited by Mel Scult Volume I: 1913–1934 (Detroit: Wayne State University Press, 1999), 560 pp. Volume II: 1934–1941 (Detroit: Wayne State University Press, 2016), 470 pp. Volume III: 1942–1951 (Detroit: Wayne State University Press, 2020), 456 pp. Students of twentieth-century American Judaism and Jewish theology have long sought to understand the broad thinking and depth of influence of Mordecai M. Kaplan—one of the most prolific writers and theologians and rabbis of American Judaism. Kaplan’s teaching and writing had a long-term impact not only on generations of rabbis and educators --but on non-Orthodox Jews in general. It is not an exaggeration to say that much of how American Jews understand Judaism, Jewish life, the Jewish people, and Zionism is through the lenses and language that Kaplan created. 1 With more than sixty years of Kaplan’s many published works and recorded lectures, we have already had abundant material on all the major questions of Jewish life over the course of more than 70 years. In addition, we can even find his handwritten master’s thesis at Columbia University, submitted in 1902 and at the archives of the Jewish Theological Seminary, the Reconstructionist Rabbinical College and the American Jewish Archives, we find additional letters and papers as well as the decades of diaries by a man who wrote nearly every day for over 70 years But even with that abundance of materials, we were still missing something very