It's pronounced "Sen".

“Sex and Gender in Simone de Beauvoir’s Second Sex”

Yeah okay a lot of this is a response to Beauvoir and I’ll get to some of her stuff later but Butler’s argument in essence:

1. People naturally categorize other people, as a part of the way the human mind works. It is not necessarily unreasonable, then, to try seek out the commonalities between the members of that category, so that you can “prove” what exactly the requirements are for belonging to said category.
2. However, the commonalities that you find as “proof” depends entirely upon the preconceived notions that drove you to place those particular people into that category to begin with. For example, if you start out believing that a requirement of being a “real man” is having a penis, then when you turn around to look at this group of subjectively-determined “real men” for “proof of who is a real man,” you will only see people with penises, thereby “confirming” your original belief that real men require a penis.
3. In short, by attempting to define any group of people, you are drawing definitions without knowing that these definitions depend completely upon the boundaries you have already subconsciously drawn. So, this entire process is completely arbitrary and untenable as proof of anything in an argumentative position.
4. Therefore, Butler argues that not only is gender socially constructed and impossible to truly delineate or define in physical terms, but also biological sex is socially constructed as well. After all, intersex individuals, people with “wrong” hormones, “wrong” chromosomes, or lingering “wrong” organs that never fully developed exist more commonly than you think. So saying “well, a biological male is someone whose organs, chromosomes, and hormones are like so” not only self-defines the category (as determined in point 3), but also is completely socially-determined and arbitrary. Who sets the rule that says that this particular characteristic is what makes you male, female, or in-between? Society.