Let's say I was to tell you I am a human male. While this sentence is short and simple, the amount of information you could glean from it is a potential goldmine, assuming you are starting from a position of near total ignorance about me. First, it provides you with my species identification. In the most general sense, that lets you know what types of organisms in the world I am capable of potentially reproducing with (to produce reproductively-viable offspring in turn). In addition to that rather concrete fact, you also learn about my likely preferences. Just as humans share a great deal of genes in common (which is why we can reproduce with one another), we also share a large number of general preferences and traits in common (as these are determined heavily by our genes). For instance, you likely learn that I enjoy the taste of fruit, that I make my way around the world on two feet, and that hair continuously grows from the top of my head but much more sparingly on the rest of my body, among many other things. While these probable traits might not hold true for me in particular—perhaps I am totally hairless/covered in hair, have no legs, and find fruit vile—they do hold for humans more generally, so you can make some fairly-educated guesses as to what I'm like in many regards even if you know nothing else about me as a person. It's not a perfect system, but you'll do better on average with this information than you would if you didn't have it. To make the point crystal clear, imagine trying to figure out what kind of things I liked if you didn't even know my species.
When you learn that I am a male, you learn something concrete about the sex chromosomes in my body: specifically, that I have an XY configuration and tend to produce particular types of gametes. In addition to that concrete fact, you also learn about my likely traits and preferences. Just as humans share a lot of traits in common, males tend to share more traits in common with each other than they do with females (and vice versa). For instance, you likely learn that the distribution of muscle mass in my upper body is more substantial than females, that I have a general willingness to relax my standards when it comes to casual sex, that I have a penis, and that I'm statistically more likely to murder you than a female (I'm also more likely to be murdered myself, for the record). Again, while these might not all hold true for me specifically, if you knew nothing else about me, you could still make some educated guesses as to what I enjoy and my probable behavior because of my group membership.
One general point I hope these examples illuminate is that, to talk meaningfully about a topic, we need to have a clear sense for our terms. Once we know what the terms "human" and "male" mean, we can begin to learn a lot about what membership in those groups entail. We can learn quite a bit about deviations from those general commonalities as well. For instance, some people might have an XY set of chromosomes and no penis. This would pose a biological mystery to us, while someone having an XX set and no penis would pose much less of one. The ability to consistently apply a definition, even an arbitrary one, is the first step in being able to say something useful about a topic. Without clear boundary conditions on what we're talking about, you can end up with people talking about entirely different concepts using the same term. This yields unproductive discussions and is something to be avoided if you're looking to cut down on wasted time.
Speaking of unproductive discussions, I've seen a lot of metaphorical ink spilled over the concept of gender; a term that is supposed to be distinct from sex, yet is highly related to it. According to many of the sources one might consult, sex is supposed to refer to biological features (as above), while gender is supposed to refer, "...to either social roles based on the sex of the person (gender role) or personal identification of one's own gender based on an internal awareness (gender identity)." I wanted to discuss the latter portion of that gender definition today: the one referring to people's feelings about their gender. Specifically, I've been getting the growing sense that this definition is not particularly useful. In essence, I'm not sure it really refers to anything in particular and, accordingly, doesn't help advance our understanding of much in the world. To understand why, let's take a quick trip through some interesting current events.
In this recent controversy, a woman called Rachel Dolezal claimed her racial identity was black. The one complicating factor in her story is that she was born to white parents. Again, there's been a lot of metaphorical ink spilled over the issue (including the recent mudslinging directed at Rebecca Tuvel who published a paper on the matter), with most of the discussions seemingly unproductive and, from what I can gather, mean-spirited. What struck me when I was reading about the issue is how little of those discussions explicitly focused on what should have been the most important, first point: how are we defining our terms when it comes to race? Those who opposed Rachel's claims to be black appear to fall back on some kind of implicit hereditary definition: that one or more of one's parents need to be black in order to consider oneself a member of that group. That's not a perfect definition as we need to then determine what makes a parent black, but it's a start. Like the definition of sex I gave above, this concept of race references some specific feature of the world that determines one racial identity and I imagine it makes intuitive sense to most people. Crucially, this definition is immune to feelings. It doesn't matter if one is happy, sad, indifferent, or anything else with respect to their ethnic heritage; it simply is what it is regardless of those feelings. In this line of thinking, Rachel is white regardless of how she feels about it, how she wears her hair, dresses, acts, or even whether we want to accept her identification as black and treat her accordingly (whatever that is supposed to entail). What she, or we, feel about her racial identity is a different matter than her heritage.
On the other side of the issue, there are people (notably Rachel herself) who think that what matters is how you feel when it comes to determining identity. If you feel black (i.e., your internal awareness tells you that you're black), then you are black, regardless of biological factors or external appearances. This idea runs into some hard definitional issues, as above: what does it mean to feel black, and how is it distinguished from other ethnic feelings? In other words, when you tell me that you feel black, what am I supposed to learn about you? Currently, that's a big blank in my mind. This definitional issue is doubly troubling in this case, however, because if one wants to say they are black because they feel black, then it seems one first needs to identify a preexisting group of black people to have any sense at all for what those group members feel like. However, if you can already identify who is and is not black from some other criteria, then it seems the feeling definition is out of place as you'd already have another definition for your term. In that case, one could just say they are white but feel like they're black (again, whatever "feeling black" is supposed to mean). I suppose they could also say they are white and feel unusual for that group, too, without needing to claim they are a member of a different ethnic group.
The same problems, I feel, apply to the gender issue despite the differences between gender and race. Beginning with the feeling definition, the parallels are clear. If someone told me they feel like a woman, a few things have to be made clear for that statement to mean anything. First, I'd need to know what being a woman feels like. In order to know what being a woman feels like, I'd need to already have identified a group of women so the information could be gathered. This means I'd need to know who was a woman and who was not in advance of learning about their specific feelings. However, if I can do that—if I can already determine who is and is not a woman—then it seems I don't need to identify them on the basis of their feelings; I would be doing so with some other criteria. Presumably, the most common criteria leveraged in such a situation would be sex: you'd go out and find a bunch of females and ask them about what it was like to be a woman. If those responses are to be meaningful, though, you need to consider "female" to equate to "woman" which, according to definitions I listed above, it does not. This leaves us in a bit of a catch-22: we need to identify women by how they feel, but we can't say how they feel until we identify them. Tricky business indeed (even forgoing the matter of claims that there are other genders).
On the other hand, let's say gender is defined by some objective criteria and is distinct from sex. So, someone might be a male because of their genetic makeup but fall under the category of "woman" because, say, their psychology has developed in a female-typical pattern for enough key traits. Perhaps enough of their metaphorical developmental dials have been turned towards the female portion. Now that's just a hypothetical example, but it should demonstrate the following point well enough: regardless of whether the male in question wants to be identified as a female or not, it wouldn't matter in terms of this definition. It might matter a whole bunch if you want to be polite and nice to them, but not for our definition. Once we had a sense for what dials, or how many of them, needed to be flipped to "female" and had a way of measuring that for a male to be considered a woman, one's internal awareness seems to be besides the point.
While this definition helps us talk more meaningfully about gender, at least in principle, it also seems like the gender term is a little unnecessary. If we're just using "man" as a synonym for "male" and "woman" as one for "female", then the entire sex/gender distinction kind of falls apart, which defeats the whole purpose. You wouldn't feel like a man; you'd feel like a male (whatever that feels like, and I say that as a male myself). Rather than calling our female-typical male a woman, we could also call him an atypical man.
The second issue with this idea nagging at me is that almost all traits do not run on a spectrum from male to female. Let's consider traits with psychological sex differences, like depression or aggression. Since females are more likely to experience depression than males, we could consider experiencing depression as something that pushes one towards the "woman" end of the gender spectrum. However, when one feels depressed, they don't feel like a woman; they feel sad and hopeless. When someone feels aggressive, they don't feel like a man; they feel angry and violent. The same kind of logic can be applied to most other traits as well, including components of personality, risk-seeking, and so on. These don't run on a spectrum between male/masculine and female/feminine, as it would make no sense to say that one has a feminine height.
If this still all sounds very confusing to you, then you're on the same page as me. As far as I've seen, it is incredibly difficult for people to verbalize anything of a formal definition or set of standards that tells us who falls into one category or the other when it comes to gender. In the absence of such a standard, it seems profitable to just discard the terms and find something better, something more precise, to use instead.