William Samuel Sadler (June 24, 1875 – April 26, 1969) was an American surgeon, self-trained psychiatrist, and author who helped publish The Urantia Book.

There he met the physician and health-food promoter John Harvey Kellogg, co-inventor of corn flakes breakfast cereal, who became his mentor.

Although he was a committed member of the Seventh-day Adventist Church for almost twenty years, he left the denomination after it disfellowshipped his wife's uncle, John Harvey Kellogg, in 1907.

Sadler extolled the value of prayer and religion but was skeptical of mediums, assisting debunker Howard Thurston, and embraced the scientific consensus on evolution.

A larger number of interested people met at Sadler's home to discuss the man's responses and to suggest additional questions.

Although it never became the basis of an organized religion, the book attracted followers who devoted themselves to its study, and the movement continued after Sadler's death.

[2][a] Despite his lack of formal education, Sadler read many books about history as a child and became a skilled public speaker at a young age.

[11] Around 1895, Sadler attended Moody Bible Institute in Chicago, Illinois, where he trained to be an evangelist, ultimately becoming an ordained minister in 1901.

[13] In San Francisco, he served as the "superintendent of young people's work" for the church's California conference and the president of a local Medical Missionary society.

[2][16][g] Sadler was an early adopter of Freudian psychoanalysis, and believed that experiences individuals have as infants play a key role in their minds as adults, although he did not accept many of Freud's ideas about sexuality or religion.

[17][18] Although Sadler was a committed Adventist for much of his early life, he stayed less involved after John Kellogg was excommunicated in 1907 in the wake of a conflict with Ellen G. White, the church's founder.

[24] As a psychiatrist, Sadler advocated an eclectic mix of techniques, applying the theories of Sigmund Freud, Carl Jung, Alfred Adler, and Adolf Meyer.

Sadler wrote several works about eugenics, endorsing and heavily borrowing from Grant's views, which posited that the "Nordic race" was superior to others.

[40] Sadler argued that alcoholism[41] and "feeblemindedness, insanity, and delinquency"[25] were hereditary traits and that those who possessed them were breeding at a much faster rate than "superior human beings".

[25] He also believed that the majority of criminals were mentally ill.[42] In 1907, Sadler began giving lectures on the Chautauqua adult-education circuit, which featured itinerant speakers discussing self-help and morality.

[43] Sadler, his wife, her sister, and a friend, formed a four-member lecture company that gave two- or three-day engagements, sometimes accompanied by an orchestra.

[24] Sadler believed that mediums were a source of false comfort and, after World War I ended, fought against the increased popularity of communication with the dead.

[24] In the 1910s and 1920s, attempting to expose purported clairvoyants became one of Sadler's favorite pastimes[j] and he regularly worked with a Northwestern University psychologist and Howard Thurston, then a prominent magician, while investigating psychics.

[53] His identity has never been confirmed;[46] Joscelyn Godwin,[54] of Colgate University, and skeptic Martin Gardner[55] posit that the sleeping man was Wilfred Kellogg, the husband of Lena's sister Anna.

[50] The forum discontinued their discussion meetings in 1942, and The Urantia Book was published in 1955; it purportedly contained information from the celestial beings who had spoken through the sleeping man.

[62] Journalist Brook Wilensky-Lanford argues in her 2011 profile of the Urantia movement that Sadler's departure from the Adventist church gave him the desire to build a new religious movement, citing the emphasis that Sadler placed on the discussion of the Garden of Eden in The Urantia Book as evidence of his desire to start anew.

[63] Sadler hoped that the content of the revelation would convince people of its worth, and did not attempt to win supporters by emphasizing its author.

[68] Hubert Wilkins, a friend of Sadler who had a keen interest in the book, contributed the initial funding for publication costs.

[79] As he grew older, Sadler generally remained in good health, with the exception of a condition that led to the removal of an eye.

[34] By the time of his death, Sadler was acclaimed for his accurate prediction of the advent of organ transplantation decades before the practice became commonplace.

[82] Gooch deems Sadler the "Moses of the Urantia movement" and casts him as "one of America's homegrown religious leaders, an original along the lines of Joseph Smith".

[84] Gooch believes there is a contradiction between Sadler's advocacy of science and reason and his support of the avant-garde theological, "inter-planetary" contents of The Urantia Book.

[85] Gardner describes Sadler's life story as "riveting" and summarizes him as an "intelligent, gifted" person who proved to be "gullible" about alleged supernatural revelations.