Graeme Archer is a medical statistician, a former winner of the Orwell Prize for blogging, and was recently a speechwriter for a Cabinet Minister.

What is a man? What is a woman? These are fairly fundamental questions. My answer: maleness, femaleness, these are cultural norms, manifest on and through a biological substrate.

The cultural norms can evolve, or be subverted, quite rapidly: everyone is free to express themselves how they wish. Walk like a man, talk like a man…if you want, or insist, like David Walliams / Emily Howard, that you’re “a lady”: that’s up to you.

Biology cannot be so subverted, not in the lifespan of individual human beings; not outside the timescale of mammalian evolution. One possesses a Y chromosome, or one does not. Shakespeare would appear to have realised something we are in danger of forgetting: that which we label as “sex” is biologically determined; that we call “gender” is a sociological construct.

I’m very aware, before we go further, that not every human being is born with such clear-cut biology. The incidence rate for intersex births is politically contentious – one of the reasons I’m writing this article, as it happens – but it’s a fact that some people are born with neither an XY nor an XX genotype, and their journey to the male or female phenotype is therefore ambiguous. Such individuals are not the topic of this piece, and some of them are medically abused, having a sex chosen for them pre-puberty, without reference to their feelings.

But the vast majority of human beings are born with clear genetic coding for either “male” or “female”. Those genotypes are our sex, in the sense that they map our trajectory from conception to physical (and sexual) maturity; this is not a matter of opinion. Before sociology (cultural norms for a society), before psychology (how individuals perceive themselves and the world they inhabit), before everything, there is human biology. Or there is nothing.

That was a fairly heavy opening, wasn’t it? I hope I haven’t lost you. I’ve certainly lost the Government, which is ready to legislate against scientific fact. Justine Greening’s answer to “What is a man?” is “Anyone who signs the appropriate government form.” Or, if you change your mind, you can be a woman too. It’s just a matter of bureaucracy; no need to get that ghastly medical patriarchy involved.

We’ll come to the negative consequences of this, but first: why is this happening?

Because well-meaning Conservatives, miserable since the election, are seeking to dispel their “nasty” tag. To do so, they’ve formed an unholy alliance with the identity politics merchants of the modern Left, who use the “LGBTQ+” label to recast society. It’s a mistake, Justine. Here’s why.

I wrote recently of my loathing for the “LGBTQ+” label. I’m a gay man: neither the adjective nor the noun are matters of opinion. What I am not is “LGBTQ+” – unpacked, that means “lesbian and gay and bisexual and transgender and queer and any genderless gender that is neither male nor female”. No-one on the planet is such a thing; it’s a political assertion, not a human being.

Most fundamentally, the elision of homosexuality and transgenderism is a category error. The former is an expression of same-sex attraction, the latter an extreme aversion to the sex of one’s birth; an individual’s psychology at war with its biological substrate. Transgenderism and homosexuality aren’t just different concepts, they are antithetical to one another, and, as I wrote, “one’s attitude to the former can’t be a function of one’s status regarding the latter.”

Andrew Sullivan points out the intellectual incoherence of “LGBTQ+” here:

“By severing the link between sex and gender completely, it [the “LGBTQ+ label] abolishes the core natural framework without which the transgender experience makes no sense at all. It’s also a subtle, if unintentional, attack on homosexuality. […] And that’s one reason the entire notion of a common “LGBT” identity is so misleading. How can a single identity comprise both the abolition of gender and at the same time its celebration?”

Homosexuality, in other words, has a physical dimension which transgenderism lacks. I can prove my same-sex orientation – and its congruence with, not opposition to, my gender – but the statement “I am the wrong gender, regardless of my biological sex”, like the “LGBTQ+” label, is an assertion. There’s no scientific observation which could support or deny such a claim.

Which is why, prior to surgery, prior to the re-writing of birth certificates, the medical (psychiatric) professions have a role to play, and governments should be cautious, and time should be allowed to pass. No-one should alter their body or gender identity without time and support; it’s callous, not kind, to suggest otherwise.

You might be thinking: the number of people involved is small, so why make a fuss? Well, for a start: if you can define your own gender and insist it supersedes your biological sex, you can surely self-define all the other dimensions of your identity.

Why not define your race – it has much less genetic basis than gender, after all? Or your IQ, your disability status, your nationality. If self-defining your ethnic heritage strikes you as farcical, why would gender be any different?

More seriously: what must it be like to be a young boy these days? Their gender is constantly belittled; too many of their homes lack fathers; the media pushes a message of not only how great women are (women are great; I just don’t need every third line in Doctor Who to remind me) but also that men are always a problem, causing wars and financial crashes and so on (that’s about right, Harriet, no?)

Now the Government wants boys to believe that their gender doesn’t matter, that it can be got rid of, should it be a nuisance. Is it any wonder that male-to-female sex operations outnumber those for female-to-male by an estimate of 3:1? You don’t have to get all “crisis in masculinity” to worry about this; just fond of men.

Everyone, including those who feel transgender, should be treated with politeness and dignity, however they choose to present themselves. This isn’t a reductive “gendered restroom” thing, an invented dividing line in some life-sapping culture war. Freedom of expression – including one’s gender persona – is a British right.

But my political response to the Government’s proposals cannot be demanded as a function of my sexuality. You can’t insist that sexual orientation and gender identity are the same thing. You can’t carve a politics on the basis of a label that describes not one single living being. And Tories, of all people, cannot pretend that a desire for kindness can overturn biological fact, or that there are no negative consequences to such a desire.

To proclaim that psychology drives biology, rather than the reverse, is to say that political will can trump scientific reality. Let the government get away with that, and you’re not at the top of a slippery slope, but careering fast towards the wall of cultural oblivion, foot hard on the pedal, screaming “the wall doesn’t exist if I say so.” How would you guess that would turn out, Justine?