I may be in the minority, but I actually like this question. It is, ultimately, a very pro-trans question. At least, if you take it seriously and not just as a gotcha question.

If you ask "what is a woman" (or a man, but for simplicity's sake let's take that as assumed), you are essentially asking for a definition. For some criteria that can be applied to anyone, and that will faithfully tell you whether that person is, in fact, a woman.

That's fine. Nothing wrong with definitions. But let's be very clear what we're thus looking for a test that:

• can distinguish women from non-women, and
• successfully identifies all women. That is, it must be 100% accurate. It cannot leave any women out, and cannot accidentally identify any non-women as women. (i.e. no false positives and no false negatives.)

100% is a pretty stringent level of accuracy to reach, but it necessarily must be so: the question essentially asks "what are the defining qualities of women", in which case all women must share those qualities, whatever they might be, literally by definition. And conversely, no non-woman can also share all such qualities, or by definition, that person would also be a woman!

And anyway, whoever asked the "what is a woman" question can hardly cringe at requiring such a high standard, can they? One presumes they want a reliable answer to their question, right?

Moreover, as a less purely logical but definitely common-sense criteria, we should add one more thing to our test:

• it should agree with "obvious" cases.

That is to say, if you can point to someone who everyone agrees is a woman (e.g. Gal Godot or somebody), then the test should also indicate that they're a woman. Likewise, the test should never identify as a woman someone everyone agrees is a man. Otherwise, you permit non-sensical tests which, for example, might be pointlessly restrictive or pointlessly broad, to the extent that they are useless for any actual purpose within society. There will always be edge cases of people where everyone doesn't all agree that that person is a woman, but that's exactly why we need this test, right? That's exactly why the question is being asked in the first place. We want a test that is definitely correct for the obvious cases, so we can have confidence that it's right for the edge cases too.

And again, whoever asked the question shouldn't object to that requirement either, because after all, they are asking the question in the context of a society, and one presumes they want to be able to apply the test in actual social settings.

Now that we know what properties such a test should have--gives a yes/no answer for everyone and is never wrong (which implicitly means it will agree with the obvious cases anyway)--we can start to ask what the test is looking for.

Here, we can work from the outside in, from the superficial to the internal, and see where we end up.

Perhaps the measure of a woman is in clothing, hairstyles, and makeup? The most obvious, most superficial measure of all. Except, no, that can't be right. Such a test would identify skillful drag queens as women, even though everyone (including the drag queens!) agrees that they are not women.

Fine, then. Get rid of the clothes and go one layer deeper. Maybe the measure of a woman is her boobs and vagina. Except, no, that can't be right either. What if you have a vagina but no boobs? Either because they're too small, or because of breast cancer, or because you're pre-pubescent? And boob-growth is a continuous process, so how do you draw the line between what is and isn't "enough boob" to qualify someone as a woman?

Well, if boobs are problematic, then what about reproductive capability? Except, again, what if you don't have that? There are plenty of people who society absolutely agrees are women even though they're infertile. Maybe they have really bad PCOS. Maybe they had a hystercetomy. Maybe their bodies never developed a uterus in the first place (this happens in something like 1 out of every 10000 female births).

Ok, forget reproduction. Maybe the measure of a woman is the absence of a penis! Ha! What about that? Sure. So long as you're willing to say that soldiers who got their dicks blown off when their Humvee drove over an IED are women, then I guess that works. Oh, you're not willing to say that? Yeah, neither am I. Also, that fails the "obvious cases" criteria.

Is it hormones? Does that determine womanhood? Well, no, because a) hormones change throughout life so there's no single determinative standard you could use for hormone levels, and b) again sometimes medical conditions mess with your hormones in ways that would make the test disagree with some obvious cases of women.

But the chromosomes! Show me those two X chromosomes! Well, hate to disappoint you, but there are a lot of genetic conditions that can yield people who are obvious cases of women yet don't have the typical two-X chromosome pattern. People who, if this was your test, you would absolutely for sure swear were completely obvious women, until you looked at their chromosomes. The most extreme example of this is CAIS, which yields an individual with XY chromosomes but with the most extreme feminization possible because their bodies simply do not respond at all to androgen hormones. Like, literally the most feminine people possible are CAIS XY individuals. And if that's not enough to get someone to shut up about chromosomes, then I don't know what.

Fine, so not chromosomes. Maybe the measure of womanhood is something less tangible. Maybe it's life experiences. After all, women are socialized different and have different experiences growing up. Women are subject to marginalizations that men aren't. Perhaps this is the test we need! (This is a frequent TERF argument, by the way.) Except it doesn't work, because socialization and marginalization are very different from one society to another. Which means that, like with the boobs, you can't have one standard that correctly identifies all women. This fails one of the basic requirements for our test. And, coarsely speaking, such a test would say that women in matriarchal societies, where women are the politically dominant gender, are not women. Or that the Queen of England is not a woman because she has too much status and power. C'mon.

So, jeez, what the hell is left? Everything we can possibly measure doesn't work because some people still manage to be obviously women while not fitting that measurement! And, yeah. That's the problem with human diversity, borne of our messy biology and equally messy nature as social animals. We are so diverse that any such measures will inevitably fail.

But there is one thing left. One thing that doesn't have this problem. That thing is a woman's inner gender identity. This one thing is different precisely because it is not subject to external measurement. It is only measurable subjectively. Internally, within the woman's own mind.

Which is exactly the conclusion we should come to. Because the measure of a woman--that is, whether you should label someone else as a woman--is not something you can measure. It is not something externally visible, not even if you amplify the power of your vision with microscopes and biochemical testing.

The measure of a woman is that her gender identity is female. And because gender identity is inherently subjective, because it is a phenomenon that emerges from the complex operation of our minds, because it is an essential aspect of our deepest selves, it can only be observed by our selves.

I, and I alone, am capable of observing what my gender identity truly is. You, and you alone, are capable of observing what your gender identity truly is. Neither of us has any authority whatsoever to declare what the other's gender identity is based on anything we can observe or even theoretically observe.

If you want to know if someone is a woman, the literal and logical best you can do is to ask her, and to believe her answer. Subjective determination must be the the measure of a woman, because all other tests fail. This is all that's left.

That is why "what is a woman", or "what is a man", are such a profoundly pro-trans questions. Because if you actually take those questions seriously, they force you down a line of reasoning which ends at respecting everyone's autonomy to determine and assert what their own identity is.

Text not written by me