"Why Adler Never Signed the Humanist Manifesto" -- Curt Collier, Leader of the Riverdale-Yonkers Society for Ethical Culture

The Humanist Manifesto is one of the most comprehensive statements of the aspirations and values of the Humanist community in the 1930's. It was signed by a list of notable thinkers and clergy. However, one name was noticeably absent; Felix Adler's. Why didn't Adler sign the document, and what does this act teach us about what he considered the future direction of our movement?