Adler had trained for the Reform Jewish rabbinate before founding Ethical Culture, and the Oxford Handbook of Atheism describes his break as a considered departure rather than a rejection of ethical seriousness itself, Adler concluding that shared ethical practice, not shared theology, was the ground a religious community actually needed to be built on. From the single New York society, Ethical Culture grew into a federated movement, the American Ethical Union, coordinating additional societies founded in other American cities across the following decades, with Adler's own Creed and Deed recording his conviction that the model could extend well beyond any one congregation's membership. The movement's emphasis on deed translated directly into a record of practical social reform: Ethical Culture societies were early supporters of the settlement house movement, founded some of the first free kindergartens in the United States, and Adler himself was among the founding members of the National Association for the Advancement of Colored People in 1909. As organised humanism grew as a wider movement across the twentieth century, Ethical Culture came to be counted, alongside newer explicitly humanist and atheist bodies, as one of its constituent branches, its own deed-before-creed principle predating the Humanist Manifesto by more than half a century but sharing its core commitment to a non-theistic, ethically grounded religious life.