 No topic is more central to feminist philosophy than sex and gender, but even here many variations on the theme flourish. Where analytic feminism, with its critique of essentialism, holds the sex/gender distinction practically as an article of faith (see the entry on  feminist perspectives on sex and gender  and Chanter 2009), Continental feminists tend to suspect either (1) that even the supposedly purely biological category of sex is itself socially constituted (Butler 1990 and 1993 or (2) that sexual difference itself needs to be valued and theorized (see especially Cixous 1976 and Irigaray 1974.