I respect Judith Butler – however, amicus Plato, sed magis amica veritas.
The claim that sexual differences, and the body generally, as well as agency or personhood, are “socially constructed” is incoherent and misleading. On the contrary, it seems virtually self-evident that sexual differences (and many other features of the body) are not social constructs.
A subsidiary thesis is that the mechanism by which social construction takes place is “power,” and that seems dubious as well. Surely a great deal of social construction takes the form of interactions that are entirely voluntary and mutually beneficial.
Moreover, the metaphor of construction is misleading, because social interaction is really nothing like building, fabricating, or making. Interacting with others is more about reaching an understanding, acquiring and exercising skills or know-how, and engaging in expressive communicative action.
Butler’s position is that what she calls “the sexed body” is not only biologically determined but is also shaped by normative expectations, “power,” institutions, and so on. On top of the social construction of the sexed body, there are also “cultural meanings that the sexed body assumes,” and that’s “gender.”
Thus, in Gender Trouble she suggests that “this construct called ‘sex’ is as culturally constructed as gender.” In Bodies That Matter she suggests that “medical interpellation … shifts an infant from an ‘it’ to a ‘she’ or a ‘he’.” A doctor’s report that a newborn is a boy or a girl (that’s what a “medical interpellation” is) is said to be a “performative speech act,” and sex is alleged to be “assigned” (not reported) in the way that a ship is christened. A newborn’s sex is said to be constituted by the alleged performative, as if the doctor really means to say “I hereby assign this infant the sex of female.” But, of course, you can assign anything you like to any category you like; it doesn’t mean the thing actually belongs in that category.
Discussion of this topic can be difficult because the social constructivist tends to confuse the fact that the categories (or “constructs”) of male and female are social creations with the assertion that the objects of those categories are socially constructed. The concept of a microbe was constructed in a society, but microbes were not. To be truly socially constructed in the sense the constructivist would like to take it, the object of the category must belong to a society. Thus, “teacher” is socially constructed because if there were no societies then there wouldn’t be any teachers. But it’s false, or at best misleading, to say that a doctor’s report “shifts an infant” from one sex to another. Neither the infant nor its sex is socially constructed.
The thesis that sex is socially constructed is an equivocation between categories and their objects, nothing more.