This week, to the horror of student campaigners, Brendan O’Neill was invited to speak at a dinner at The Queen’s College, Oxford. This is what he said.

It is my sincerely held belief that a man can never become a woman. That no matter how many hormones he takes, or operations he has, or fabulous outfits he buys, a person who was born male can never become female. I accept a man can be a trans-woman. I accept the right of every man to claim to be a woman. And to change his name to a woman’s name, if he likes. And these trans-women should of course enjoy the same rights as every other citizen: the right to vote, the right to free speech, the right to work. But to my mind, they are not women. The slogan ‘Trans women are women’ is a lie. This is my sincerely held belief.

Recently, however, this belief has become virtually unutterable in respectable society. It has become tantamount to heresy. To deny that men can become women is the modern equivalent of denying that a wafer of bread and a cup of wine became the flesh and blood of Christ during Mass. If you deny the magic of transgenderism, you will be subjected to a similar wild-eyed fury that was once visited upon those who denied the magic of transubstantiation. There is a religious-style zeal to the protection of transgenderism from criticism or denial or blasphemy. The word ‘transphobia’ is used to demonise the belief that men cannot become women. Fighting transphobia isn’t about ending discrimination against trans people – it is about silencing moral views that are now considered unacceptable; it is about turning certain beliefs into heresies. ‘Transphobia’ is really a new word for blasphemy. To accuse someone of ‘transphobia’ is to accuse them of having sinned or libelled against the new orthodoxy that says gender is fluid, some men have female brains, binaries are a myth, and so on. Make no mistake: transphobic means heretic.

Witness how feminists who question the magic of transgenderism are hounded off campuses and blacklisted by the NUS. These feminists are referred to by the most awful names online: bitches, cunts, whores. Or TERFs. TERF, meaning trans-exclusionary radical feminist, has become the most common insult hurled at these blasphemous women. TERFs are blacklisted by student officials, most recently at Bristol University. They have been physically prevented by trans activists from holding public meetings. They have been violently attacked: last year trans activists assaulted a 60-year-old grandmother, or TERF, to give her the dehumanising name they gave her as they punched her in the face. A TERF is a witch. That is really what TERF means: troublesome woman, uppity woman, defiant woman, heretic. Just as the medieval fear and fury with witches was driven by the Church’s urge to root out heresy, to discover and punish unorthodox thinking, so today’s blacklisting and assaulting of TERFs is driven by the establishment’s intolerance of dissent towards the new religiosity of genderfluidity. Especially among women. Religious-style wars on heresy always hate female dissenters even more than male ones. That the TERF-finders, like the witch-finders of old, hate female heretics more than male ones – more than me, for example – is testament both to the trans movement’s intolerance of any view of womanhood that differs to its own elastic, eccentric view of womanhood, and also to its commonalities with earlier movements against witch-like female defiance of religious diktat.

So, recently we had the spectacle of 300 female members of the Labour Party resigning in protest at the party’s decision to include people who were born male on all-women shortlists. And other party members, including male ones, cheered as the women left. ‘Get the TERFs out’, they tweeted. That is, cast the witches out. Expel them. Heretics not welcome. That many left-wing men laugh at these women’s concerns, or approve of the censorship of their ideas, or conspire in the demonisation of them as TERFs, suggests the ideology of transgenderism has a strong streak of misogyny. Indeed, trans activism looks increasingly like misogyny in drag. Witness, also, how criticism of the trans ideology is written off not only as wrong, but as dangerous, as morally corrupted and morally corrupting. Apparently, these people’s beliefs are a kind of poison, liable to pollute souls and minds and maybe even cause young trans people to kill themselves. A certain point of view, the point of view that says you cannot magically change sex, is imbued with awesome, devastating power, the power to kill.

This, too, is in keeping with earlier crusades against heresy. Then, as now, unorthodox thinking, whether it went against Vatican law or raised questions about Biblical scripture, was treated not only as ill informed but as ill, a sickness, and a sickness that might spread. As one historical account puts it, people and sometimes entire communities were viewed as being ‘infected with heresy’. Today, that profoundly censorious idea finds expression in the war on the blasphemy of transphobia. As one headline put it recently, ‘Transphobia is the mental illness, not transsexuality’. Or as a writer for the Los Angeles Times said, it is the critics of transgenderism who are ‘truly sick’. That is, their ideas are a contagion that cause harm and sometimes death. They are infected with heresy, and they infect others with their heresy. What we are witnessing is a classic act of demonology: the transformation of an entire group of people, trans-critical people, into demons. Through demonology, censorship and occasionally violence, the belief that you cannot magically change sex – a belief I hold to – has been turned from an acceptable point of view into a heresy you utter at your risk. I find this fast and unforgiving transformation of a moral view into mortal sin fascinating, because it is a modern case study in the making of witches, and in the imposition of orthodoxy. It deserves study, this moral and physical assault on an idea, because it represents a 21st-century version of the diseasing of critical thinking that was more commonplace in darker moments in history.

As I have watched all of this unfold, I started to ask myself a question: what happens when you become a heretic? What happens when, through no fault of your own, your beliefs are deemed to be dangerous? What happens when the parameters of acceptable thinking shrink, suddenly and violently, and you find yourself outside of them, an intellectual leper? What should this newly christened heretic do? It seems pretty clear to me that he or she has a choice. A difficult choice, but a choice nonetheless. At this point it’s worth noting that heresy actually means choice. The word heresy comes from the Greek for ‘choice’, for ‘the chosen thing’. To be a heretic is to make a choice – the wrong choice, in the view of the guardians of orthodoxy. And the choice faced by today’s accidental heretics, by those who woke one day to find that the thing they have been saying for years is now verboten, is this: you either accept your status as ‘evil’ and silence yourself for the supposed good of social stability; or you reject this status and continue to utter your so-called heresy because you believe, sincerely, that it is true. This is your choice, this is your heresy.

And I expect it will not surprise many of you here tonight that my advice is to do the latter: continue to speak your heresy, and damn the consequences. You should do this for two reasons. First, because it will be good for you as an individual. And secondly, because it will be good for society as a whole. Of course it isn’t only trans-critical thinking that has been rebranded heresy. The industry of demonology has been working overtime of late, busy discovering new demons, busy delegitimising certain beliefs. The language of demonology is rampant in public life today. The two most common brands imposed on those judged to hold heretical beliefs are ‘phobic‘ and ‘denier’. They are fascinating terms. The first, ‘phobic’, speaks to the treatment of certain views as irrational fears, as forms of mental illness, essentially. And the second, ‘denier’, echoes precisely the terminology used against those who were dragged before the Inquisition. They, too, were deniers: deniers of the light of Christ.

So if you criticise trans thinking, you are transphobic. If you think gay marriage is not a good idea, and that the institution of marriage plays a specific social role best filled by heterosexual couples, you are homophobic. Criticise Islam, and you’re Islamophobic. Indeed, when the Runnymede Trust first popularised the term ‘Islamophobia’, in the 1990s, it included in its definition any expression that treats Islam as ‘inferior to Western values’. So to make a particular moral judgement, in this case that Western ideals are better than Islamic ones, is to be unstable, diseased. This is a clear example of the language of demonology being used to make a heresy out of a perfectly legitimate moral view. Worry about mass immigration, and you’re xenophobic. Oppose the EU and maybe you suffer from the mental malaise of Europhobia. One pro-EU observer says Europhobia is a species of racism that is ‘alien to the postwar European culture’. And so a political perspective – opposition to the Brussels oligarchy – is refashioned as irrationalism.

Alongside the phobics, there are the deniers. If phobics are morally ill, deniers are straight-up sinful. The most commonly made accusation of denial is against climate-change deniers. Anyone who questions not only the science of climate change, but also the political proposals put forward for dealing with environmental problems – which usually involve discouraging large-scale development – is likely to be denounced as a ‘denier’. And again, their words are treated not only as wrong but as morally depraved, even as a threat to life on Earth. Their ideas are imbued with a devil-like power to corrupt and harm existence itself. So it was that one environmentalist said there should be ‘international criminal tribunals’ for these deniers, where they might be made to ‘answer for their crimes’. That is, an Inquisition. Their words are crimes, their ideas a kind of moral pollution which might be even more dangerous than industrial pollution itself. They are heretics as surely as ‘Christ deniers’ were heretics. Those who have conspired in this creation of a scientific orthodoxy that mere mortals question at their peril should reflect on the fact that science itself is heresy. Or it certainly starts as heresy. In the words of Isaac Asimov, ‘Some of the greatest names in science have been… heretics. Startling scientific advances usually begin as heresies.’ That science and its adherents now contribute to the policing and punishment of heresy represents an abandonment of the openness to rebuke and falsification that makes science such an important endeavour in the first place.