Havelock Ellis

British physician and writer who was the first major English-language sexologist — writing the encyclopedic Studies in the Psychology of Sex that normalized previously taboo sexual topics.

Studies in the Psychology of Sex (7 vols): a comprehensive survey of sexual behavior — homosexuality (inverted sexuality), erotic symbolism, auto-erotism, sexual inversion — treating sexuality as a natural phenomenon deserving scientific study. Was among the first to argue that homosexuality is congenital rather than a perversion. Influenced the early sex reform movement.