(1859–1939) English author of Studies in the Psychology of Sex (1903–28). Until 1935, Ellis's Studies, which argued that erotic dreams, foreplay, and masturbation were normal, were legally available only to medical professionals. He believed that birth control was the key to sexual liberation. He believed sex to be natural and good, and asked, "Why … should people be afraid of rousing passions, which, after all, are the great driving forces of human life?" Ellis was an important mentor to Margaret Sanger.