Sexual inversion was a nineteenth-century theory of homosexuality best described by the pioneering sexologist Karl Heinrich Ulrichs (1825–1895) as anima muliebris virili corpore incluse, or, a woman's soul confined within a man's body. In the nineteenth century, sexual inversion, homosexuality, and antipathic sexuality were interchangeable terms. The "inversion" in sexual inversion referred to the inverted, or upside-down, quality of a body that did not reflect the "true" essence of its possessor. The truth of the invert was inside rather than on the surface; thus a male invert was "really" a woman, and should be allowed to express a female gender, and a female invert was "really" a man, and should be allowed to dress and live as one. Inversion also referred to the ways in which such bodies inverted the laws of nature, which supposedly decreed that male bodies should desire female sexual partners instead of male ones, and vice versa. The theory of sexual inversion maintained conventional categories of sexuality and gender and did not allow one to be divided from the other. Inversion meant that a man's homosexual desires, effeminacy, or both did not challenge masculine gender or heterosexual sexual norms; rather, a perfectly normal heterosexual woman with a feminine gender was trapped inside him, yearning to come out.
When sex pioneer Havelock Ellis published his landmark Sexual Inversion in 1897, he defined congenital sexual inversion on the very first page of his book as "sexual instinct turned by inborn constitutional abnormality towards persons of the same sex." By 1905, however, Sigmund Freud's Three Essays on the Theory of Sexuality posited the innate bisexuality of all human beings and began to theorize sexuality more as an unruly drive in need of channeling than an essence or nature. Although Freud put gender almost entirely in the service of sexual desire, his work began the privileging of sexuality over gender that would eventually uncouple one from the other almost entirely, and lead to the call by midcentury homosexual and lesbian activists to end the stereotyping of gay men as effeminate and lesbians as masculine. The English novelist Radclyffe Hall attempted to revive the concept of sexual inversion in her landmark 1928 novel, The Well of Loneliness, in order to argue that lesbians and homosexual men were really normal people trapped in the wrong bodies, but by then sexual inversion was already outdated, and for the next sixty years it remained out of favor as little more than an antiquated theory of lesbian and gay identity.
Sexual inversion found new favor among transgender activists and scholars in the late 1980s and 1990s, in large part because sexual inversion privileged gender as much or more than sexual desire as grounds for a personal identity and identification. The notion that one's true self is trapped inside a body that does not reflect it is the essential definition of sexual inversion, though in the early twenty-first century gender inversion might be a more accurate term. Sexual inversion, now called transgender identity, offers an explanation as to why changing the gender of one's body through cross-dressing, hormones, and surgery feels "right" to so many transgender people. It seems to explain to many women why they feel like men, and not women or lesbians, and explains to many men who feel like women, and not gay men, why they are happier acting and dressing like women. In the early twenty-first century, transgender identity refers almost exclusively to gender in a way that sexual inversion, which was still tied to sexual expression, did not. As a result, where once candidates for sexual reassignment surgery had to convince doctors that they wanted to be heterosexual and gender-normative, one can now be a gay genderqueer transman as well as a straight one, or a transgender drag queen or transgender lesbian as well as a heterosexual woman.
Ellis, Havelock. 1897. Sexual Inversion. London: Wilson and Macmillan.
Freud, Sigmund. 2000. Three Essays on the Theory of Sexuality, trans. and ed. James Strachey. New York: Basic. (Orig. pub. 1905.)
Halberstam, Judith. 1998. Female Masculinity. Durham, NC: Duke University Press.