For this reason, accounts of the original transformation of sex into gender by means of the incest taboo have proven particularly useful to feminists. Butler revisits three of the most popular: the anthropologist Claude Lévi-Strauss's anthropological structuralism, in which the incest taboo necessitates a kinship structure governed by the exchange of women; Joan Riviere's psychoanalytic description of "womanliness as a masquerade" that hides masculine identification and therefore also conceals a desire for another woman; and Sigmund Freud's psychoanalytic explanation of mourning and melancholia, in which loss prompts the ego to incorporate attributes of the lost loved one, in which cathexis becomes identification. Butler extends these accounts of gender identification in order to emphasize the productive or performative aspects of gender. With Lévi-Strauss, they suggest that incest is "a pervasive cultural fantasy" and that the presence of the taboo generates these desires; with Riviere, they state that mimicry and masquerade form the "essence" of gender; with Freud, they assert that "gender identification is a kind of melancholia in which the sex of the prohibited object is internalized as a prohibition" (63) and therefore that "same-sexed gender identification" depends on an unresolved (but simultaneously forgotten) homosexual cathexis (with the father, not the mother, of the Oedipal myth). For Butler, "heterosexual melancholy is culturally instituted as the price of stable gender identities" (70) and for heterosexuality to remain stable, it demands the notion of homosexuality, which remains prohibited but necessarily within the bounds of culture. Finally, they point again to the productivity of the incest taboo, a law which generates and regulates approved heterosexuality and subversive homosexuality, neither of which exists before the law. In response to the work of the psychoanalyst Jacques Lacan that posited a paternal Symbolic order and a repression of the "feminine" required for language and culture, Julia Kristeva added women back into the narrative by claiming that poetic language—the "semiotic"—was a surfacing of the maternal body in writing, uncontrolled by the paternal logos. For Kristeva, poetic writing and maternity are the sole culturally permissible ways for women to return to the maternal body that bore them, and female homosexuality is an impossibility, a near psychosis. Butler criticizes Kristeva, claiming that her insistence on a "maternal" that precedes culture and on poetry as a return to the maternal body is essentialist: "Kristeva conceptualizes this maternal instinct as having an ontological status prior to the paternal law, but she fails