Kaplan was dissatisfied with traditional rituals and prayer, and sought to find ways to make them more meaningful to modern Jews. In, 1941 he wrote a controversial Reconstructionist Haggadah, for which he received criticism from colleagues at JTS. However, he this did not stop him from publishing the Reconstructionist Sabbath Prayer Book 1945, in which, among other unorthodoxies, he denied the literal accuracy of the biblical text. As a result, he was excommunicated by the Union of Orthodox Rabbis of the United States and Canada, who held a herem ceremony at which his prayer book was burned.
Kaplan was dissatisfied with traditional rituals and prayer, and sought to find wa,ys to make them more meaningful to modern Jews. In, 1941 he wrote a controversial Reconstructionist Haggadah, for which he received criticism from colleagues at JTS. However he this did not stop him from publishing the Reconstructionist Sabbath Prayer Book 1945, in which, among other unorthodoxies, he denied the literal accuracy of the biblical text. As a result, he was excommunicated by the Union of Orthodox Rabbis of the United States and Canada, who held a herem ceremony at which his prayer book was burned.