Answer
Ira Eisenstein, Mordecai Kaplan's son-in-law, carried forward his work in the Reconstructionist movement. He served as the editor of the movement's journal, Reconstructionist, and as president of the Reconstructionist Rabbinical College. He also wrote several books on Reconstructionist Judaism, including A Philosopher of Judaism (1961) and The Meanings of God in Modern Jewish Thought (1969).