There is no requirement for there to be edge cases or thinsg to be neat - especially when severe development issues are involved. What we can say is that a sex is a strict category based on a reproductive role around a gamete type. That is a sex by definition.
And we can say that we can classify almost all people trivially with a sex - and a tiny fraction of others perhaps with a little medical investigation. You have come up with no convincing and rational argument against this.
The argument against that is very simple: you still can’t define what your criteria are for sex identification. No amount of “medical investigation” can help you if you don’t know what you’re looking for in the first place.
Your argument appears to be because we might struggle to say *how* we recognise a person as female we must conclude we cannot. But as I have shown you, we can recognise who is male and female very reliably so the "how" is rather redundant.
For example, the majority of people recognise the left face as male and the right face as female. But ask them to explain how they know this and they will stumble. Our brains are deeply wired to recognise the sex of a person.
But as for medical intervention, we are looking for evidence of which of the two sex development pathways an individual has undergone.
Yes—until you get down to the edge cases. When you look at an individual’s unique constellation of characteristics and say “I think this is male,” but someone else says “no, I’d say this person is closer to female.” And you have no objective definition to resolve that difference of opinion.
You might also, at that point, consider zooming out and asking how much it really means to assign someone a discrete sex when it takes such an arbitrary judgment call to tip the scales.
Let's imagine there is indeed an arbitrary judgement call required to classify some people. What percentage of people do you think this applies to? Can you start putting some meat on your skeleton with claims that can be tested against the literature?
In a medical context, a very, very small percentage. In the context of guarding the washrooms at Wembley against trans invaders without literally looking inside people’s pants, high enough that you’re guaranteed to make a lot of mistakes and do a lot of damage to civil society in the process.
So, you accept almost everyone really is male or female objectively? You just worry that we might mistakes in having a bathroom policy.
Now for keeping men out of women's spaces, there are false negatives (mistaking a man for a woman) and false positives (mistaking a woman for a man). Starting with false negatives, if a man attempts to be abusive and enter a women's protected space, how often women not recognise him as a man?
Coherence of opinion is not objectivity. It just means that there are cases where no one disagrees with the conclusion, so we don’t have to prove it. (That’s why your predilection for imagining people’s parents having sex doesn’t actually answer the question.)
Gibberish.