2. The basic fact about gender in the second sense is that people are so divided—that by nature (i.e. barring disorder or injury) one's body will be in possession of one set of organs or the other. There are two basic kinds of human: the male kind and the female kind. These genera, as a rule, divide the species.
3. Supposing one were to come upon a set of humans without prior knowledge of such things, one would quickly discover that these two sorts exist, and that various attributes follow for the most part from membership in one sort or another. Certain bone structures, certain musculatures, certain patterns of maturation, certain distributions of personalities and aptitudes, and so on.
4. Thinking about the two sorts of humans and what defines them is made more difficult by the fact that humans are social and intelligent. We develop communal practices and ideas around stable features of our lives, and so the distinction between the two sorts of human is always part of a rich and complex network of behaviors, expressions, and expectations.
5. For various reasons, we humans (at least in the United States) have of late become fixated on the distinction between what is "natural" and what is "not natural". We spend a lot of time trying to discover the dividing line between what is an unchosen feature of our existence and what is a malleable construct imposed by self or society. One of the targets of this distinction is the highly colorful set of social relations and practices that have been built up around the two sorts, male and female.
6. Now it is obvious to anyone who has studied history that many features of the behavior and social positioning of the two sorts are contingent and not necessary—that they can and do change over time, and that they vary widely from place to place. This is true of dress, of standards of etiquette, of treatment under the law, and so on. Because of this fact (along with a number of other factors, which I won't get into here) there is an impulse to say that gender, the distinction of humans into the two kinds with their attendant social behavior and expectations, is in some way not natural.
7. The claim that gender is not natural is based on a reduction of the natural aspect to merely the possession of various organs. There are facts about bodies, the idea goes, but that's where nature stops. The disposition of personalities, the performance of various social behaviors, etc., is not part of nature. It is disconnected and arbitrary. While the physical presence of organs is natural, the arrangement of behaviors is "socially constructed".
8. The problem is that the distinction between what is "socially constructed" (note that the term is dangerous here, since it makes it sound as if the things in question were produced by positive design or social engineering) and what is "natural" or "essential" or necessary is not so easily made. Any sane person will recognize that certain features of personality and aptitude are distributed differently among the two kinds, in a way that is not likely to have been caused merely by social convention.
9. Social conventions regarding "male" and "female" are, in general, like many other social conventions—the accommodation of a natural set of facts about humans to a particular set of parameters. The accommodation may be disordered, or it may be beneficial. It may be highly developed or very primitive. It can have a strong moral dimension, or it can be morally indifferent. But the social convention develops as an expression of a set of natural features, features which tend to be sufficiently complex in their manifestation and distribution that they cannot be known and reduced to simple law by abstract reasoning. Custom legislates around such things in a way that the human mind could not.
10. That a salt crystal has this shape rather than that one will be a matter of its circumstances, but in either case the particular shape of the salt crystal, the orientation of its faces, its color, and many other features remain expressions of the structure and nature of the salt itself. As with salt crystals, so with the behaviors and expectations surrounding the distinction between the two kinds of human. Gender norms may differ between times and places, and may differ in a way that is more or less revealing of human nature, but they tend in general to remain expressions of something real in our nature.
11. It is for this reason that I believe in what could be called "gender essentialism". Not that dresses are essentially to be worn by women, or that cars are essentially to be loved by men, but that the nature and meaning of the two sorts is better captured by a living set of behavioral norms and social customs than by a mere biological fact about what organs are hidden between one's thighs. In short, in distinguishing between the two kinds of human beings (male and female), we have to realize that the social features of the sexes are an expression (in some way natural) of the underlying material differences between their bodies.