 Keen was a theistic evolutionist.In 1922, he authored the book "I Believe in God and in Evolution".He received honorary degrees from Jefferson Medical College
and Brown, Northwestern, Toronto, Edinburgh, Yale, St. Andrews, Greifswald, and Upsala unpresident of the American Surgical Association (1898), the American Medical Association (1900), the Congress of American Physicians and Surgeons (1903), and the American Philosophical Society (after 1907).