 For Butler, sexed bodies never exist outside social meanings and how we understand gender shapes how we understand sex (1999, 139). Sexed bodies are not empty matter on which gender is constructed and sex categories are not picked out on the basis of objective features of the world. Instead, our sexed bodies are themselves discursively constructed: they are the way they are, at least to a substantial extent, because of what is attributed to sexed bodies and how they are classified (for discursive construction, see Haslanger 1995, 99). Sex assignment (calling someone female or male) is normative (Butler 1993,  1).[6]  When the doctor calls a newly born infant a girl or a boy, s/he is not making a descriptive claim, but a normative one. In fact, the doctor is performing an illocutionary speech act (see the entry on  Speech Acts).  In effect, the doctor’s utterance makes infants into girls or boys. We, then, engage in activities that make it seem as if sexes naturally come in two and that being female or male is an objective feature of the world, rather than being a consequence of certain constitutive acts (that is, rather than being performative). And this is what Butler means in saying that physical bodies never exist outside cultural and social meanings, and that sex is as socially constructed as gender. She does not deny that physical bodies exist. But, she takes our understanding of this existence to be a product of social conditioning: social conditioning makes the existence of physical bodies intelligible to us by discursively constructing sexed bodies through certain constitutive acts. (For a helpful introduction to Butler’s views, see Salih 2002.)