History and legend are crammed with cautionary tales about mad kings. The stories share a shape: the King has lost control of what wit and reason he possessed. Wild emotion rules him, but nobody dares say so, because he is the king.

And because he is the king, he gets to remake the meaning of madness, as has been the privilege of oligarchs down the centuries. He is in charge, often divinely so, and therefore, by definition, sane. Suggesting otherwise is tantamount to treason. If anyone’s crazy, it’s you for not adjusting to the new normal. It’s safest to avoid the obvious, horrifying truth, even if the guy in the gold tower is haranguing other world leaders, ranting in public about death and destruction and fake news, and threatening obliquely to nuke Iran three weeks into the job. It’s safest to pretend, for as long as possible, that the King is not mad.

The United States has its very own Mad King to cope with, even if, by some measures, they elected him. In stabler times, questions about a politician’s sanity are either offensive, irrelevant or both - usually, when people say ‘that man is mad’, what they actually mean is ‘I don’t agree with him, and I don’t like him’. These are not stable times, however, and some brave souls are already starting to raise the mental health question we’ve all been dreading because we don’t want to hear the answer.

Paying any attention to the news at all these days is like living inside a rolling panic attack, so you may have missed the fact that somewhere between the "Muslim Ban" and the utter destruction of American political precedent, thousands of mental health professionals signed a petition stating bluntly that Mr Trump is too unwell to do the job. Elsewhere, Congressman Ted Lieu of California suggested that a presidential psychiatrist be appointed without delay. This masterpiece of concern-trolling might be a play for headlines or political points, or it might be a genuine, if misguided, attempt to science up a solution to a political crisis.

A presidential psychiatrist would be a good idea if the problem at hand could be treated with some talk therapy and a handful of mood stabilisers.

The problem, however, is not that Donald Trump is mentally ill. The problem is that he is unstable, vengeful, sexually predatory, misogynistic, racist, unscrupulous, notionally in charge of the world’s most powerful country and, possibly and incidentally, mentally ill.

The problem with the mad king is not that he is simply mad - he is also dangerous and unpredictable, and that casts his curiosities in a chilling light. The inside of Mr Trump's skull is clearly an interesting place. There is no way of knowing if the demon that drove him to lie, scheme and bully his way to the White House is the same one that makes him afraid of, among other things, going down the stairs.

Mere eccentricity is rarely a problem for royalty, and is in fact encouraged. It's when these things are combined with a track record of acting out by, for example, threatening war with China, that there starts to be a bit of an issue.

Mental health problems can sometimes be an explanation for abusive or tyrannical behaviour. But they are never, ever an excuse for it. Millions of people in America manage to have serious mental health problems without becoming freewheeling authoritarian despots. In fact, people with mental health problems are far more likely to be the victims of violence than they are to perpetrate it. I can name dozens of people with serious mental health difficulties who would make far better Presidents than Mr Trump.

Well-balanced people rarely run for president, but Mr Trump is patently committed to a reading of reality that not only bears no relation to fact but erodes the entire notion of truth until everyone forced to live inside this dissociative fugue of a presidency feels as trapped as he does. No glittering tower is high enough, no golden jet fast and flashy enough, to allow Mr Trump to escape the howling wasteland of his own brain, yammering with phantoms repeating every unflattering headline in a paranoid whisper.

I don’t know what terrible things were done to Mr Trump to make him like this, but I do know that I don’t care in anything but an academic sense. There are limits to human empathy. It’s the rest of the country, and indeed the rest of the world, that I’m worried about. So it’s well past time to stop mincing words.

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Writers have been too coy when it comes to discussing mental health and this presidency. Pitfalls of language have been dug to deter us from broaching the subject - in no small part because if we get it wrong, we risk stigmatising people with mental health conditions, committing treason, or both. Which one you’re more worried about says a lot about your ethics.

The relationship between madness, power and politics is deliberately difficult to define.

Social taboos shape the words we use and do not use to describe how politics makes us feel, and how emotion shapes politics. Crazy is not the same as delusional is not the same as irrational is not the same as abusive is not the same as disturbed is not the same as unwell.

We have been shy about stating the obvious: that something is terribly and uniquely wrong with this president. His powers weaponise the problem. We can all see it. We can all feel it, too. Donald Trump is the walking, talking, hate-tweeting embodiment of the howling identity crisis afflicting the entire United States.

And it’s affecting everyone. As Andrew Sullivan observed: ’This is a fundamental reason why so many of us have been so unsettled, anxious, and near panic these past few months. It is not so much this president’s agenda. That always changes from administration to administration. It is that when the linchpin of an entire country is literally delusional, clinically deceptive, and responds to any attempt to correct the record with rage and vengeance, everyone is always on edge. There is no anchor any more. At the core of the administration of the most powerful country on earth, there is, instead, madness.”

We need to talk about mental health and power, and we need to be very careful about how we do so. In these edgy, existentially frantic times, we must be specific. Terms like "schizophrenic", "narcissist", "mentally ill" should only be used, unless there’s a good reason otherwise, to mean exactly what they say. Don’t use someone else’s diagnosis as a lazy metaphor. The DSM-5 is not a work of political theory. When I point out, for example, that the president is behaving like a narcissistic sociopath, I mean precisely that. The only reason I’m not saying that he is one is that I have not seen his medical records, and it’s rude to fling diagnoses around like rotten fruit.

Then there are some words that that commonly refer to both medical and social phenomena - anxious, demented, depressed, manic. Those are to be used responsibly. So when I say, for example that Donald Trump is signing executive orders in the way my bipolar friends go on shopping benders when they’re at the crunchy end of a manic spree, I am not actually suggesting that the president is bipolar. I'm saying he's acting like someone does when they’re in that state and not managing it responsibly. To be clear, being bipolar would not make him unfit to serve. Winston Churchill is widely considered to have been bipolar.

Lastly, there are words like ‘mad’, ‘disturbed’, ‘raving’, ‘frantic’ and ’deranged’, all of which describe ways of behaving that can crop up whatever a person’s state of mental health. The word ‘crazy’, for example means someone or something who is or appears to be out of control of their emotions. They may or may not also be mentally ill.

‘Mad’ is the most interesting one of all. It refers both to a person who has lost touch with reality - ‘he’s mad as a march hare!’ - and to a person overwhelmed with rage - ‘he’s mad as hell and he’s not going to take it anymore!’. The question is not whether a given leader is mentally ill. Mental illness does not make a person unfit to serve. How you manage it does.

The question is: is Mr Trump mad? Yes. Yes he is. Donald Trump, the 45th President of the United States, is quite mad. You know it. I know it. It has been obvious for quite some time.

We need to get used to saying it. It’s a hard thing to say. It’s a difficult thing to contemplate. But these are surreal times where the words we use shape a reality that is being violently remade around us, and it is very, very important that we say what we mean.

So we are allowed to say that Donald Trump is crazy. We are allowed to say that he is a madman. We are allowed to say that he appears far too unstable and vengeful and out of control to hold the office he has been elected to. In fact, we must say so, because only when we call the problem by its name can we work out what to do next.

The Mad King story has a moral, and it's not aimed at royalty. It's aimed at the rest of us. It's a warning about indulging the neuroses of power, a warning about the practical and systemic costs of allowing a leader's faculties to run wild. It’s a warning about what happens when we let dangerous madmen remake our reality.

It would be senseless to ignore the warning - especially as Donald Trump is more than just any old Mad King.

Kings don't become kings because they are mad, but Trump was anointed precisely because he is the personification of the most dangerous disturbances his nation nurses at its traumatised core. He is the atavistic monster of the American id in an orange skinsack, and that is exactly why people voted for him.

America legitimised its pain by affording it high office. That was a terrible mistake America has not yet faced up the magnitude of that mistake, but it will have to do so, and soon, because this is a crisis that cannot be solved by talk alone.

The president might be mentally ill. I don’t know. I don’t care. The president is definitely a dangerous madman, and it’s not him that needs healing. It’s the country.