Good luck. I've asked him three times to define "female" and he ignored me while answering my other points. He clearly doesn't think he can do it.
Apologies. I was intending to provide an answer to this, but it was a bit longer than the usual banter, and, well, I kinda forgot
I assume you're asking about this:
But biological sex is not a social aspect. How do you define "female" or "male", then?
The short answer is this: Biological sex is defined largely the way it always has been. Chromosomes and DNA, etc etc.
The longer answer is that I see this as almost begging the question. I don't think there's good reason to treat biological sex as a useful variable for ordering our society.
The prior underlying assumption is that the biological fact of sex correlates neatly with gender is obviously incorrect. Gender roles and gender presentation, be it through general behavior or sexuality, do not neatly follow the clear cut lines of biological fact. History is littered with the victims of societies trying to force a uniformity between gender and sex, and I see no good reason to continue this barbaric practice.
Looking aside from the trans issue, we see plenty of examples where the sex=gender paradigm is being eroded. Homosexuality is becoming less taboo in civilized parts of the world. The enforcement of certain gender roles (assertive, wage earning men vs. nurturing, home-keeping women) is weakening, which is a good thing. In the absence of a top down enforced gender orthodoxy, the lines start to become very fuzzy.
We are finding, more and more, that the social definition of gender is much more nuanced and ambiguous than the straight cut lines of sex.
I see no reason why, outside of strictly clinical circumstances, that sex should be a characteristic that we use to order our society, and doing so while ignoring the complexity of gender is willful bigotry.
While there are very specific issues that have no clear answers, such as how to deal with intrinsic athletic advantages/disadvantages, or how to formalize a gender change for access to gender segregated facilities, I don't see this issues as good reason to deny the validity of trans existence.
Squeegee makes a good point here. I don't think any useful conversation is really possible so long as we have to work through the TERF gish gallop of inflammatory panic mongering about the trans menace. The attempts to smear trans inclusion as some male conspiracy perpetrated against women is patently absurd.
I'm not interested in honest, open debate when there are clearly members here who think trans people are just mentally ill sex-perverts.