The great sinologist and literary essayist, Simon Leys, once wrote that he was induced to buy G. K. Chesterton’s 1904 novel, The Napoleon of Notting Hill, as soon as he read its first words: The human race to which so many of my readers belong.

　　After so brilliant a start, the rest of the book came to him as something of a disappointment. It is difficult to maintain such a level of coruscating wit. But many of the citizens of Western democracies might nowadays say something similar about the political class that rules them: The human race, to which so many of our politicians belong. 

　　If the political class is human beings, they must have human rights, among them a right to confidentiality about their medical condition. When the electorate votes, it does not thereby deprive candidates of what everyone else is entitled to. We cannot complain that the political class has walled itself off completely from the rest of the population and granted itself unjustified immunities and privileges, and at the same time deny it the rights that everyone else has. 

　　On the other hand, given that a medical condition may seriously impair a politician’s ability to carry out the duties for which he has been elected, before or during his term of office, his state of health is not just a private matter, between him and his doctor alone. Hands, that the rod of empire might have swayd, should surely be under the control of a mind that at the least is free of the distorting effects of pathology. Once there is prima facie evidence of medical incapacity, or even mere deterioration, a person in a powerful public office becomes fair game for public medical speculation. By voluntarily seeking public office, he has given the public locus standi to intrude on at least some of his private affairs. 

　　How far down the chain of public office this may extend is a matter of judgment, as indeed is the question of how serious or intrusive a pathology must be before it is reasonable for the public to request or demand further information. Certainly, we cannot expect the political class itself to be wholly frank or honest in this regard. For politicians, partisan political calculation usually trumps, so to speak, questions of truth, morality, or even national interest. Concealment of incapacity is the natural response of the party in power, while exaggeration of the same is natural to the party in opposition.

　　If it is not altogether easy in the case of physical illness to draw a line between capacity and incapacity—what lays one man low may stimulate supreme effort by another—it becomes even more difficult when it comes to incapacity resulting from alleged mental illness. Given that everyone has their moral and political biases, and that few are capable of putting them completely aside, psychiatric diagnosis at a distance is particularly hazardous. The temptation to disqualify a detestable or detested politician on psychiatric grounds, as if this were a purely objective matter and not one of moral judgment, is strong, but should be resisted. So loose has psychiatric diagnosis become that everyone has one; the argument that someone is mentally ill is hardly more precise than are alleged analogies with fascism. 

　　In 1964, Fact magazine notoriously carried out a survey of psychiatrists, asking them whether Barry Goldwater, the Republican candidate for the presidency, was mentally fit to be president, and 1189 of 2417 who answered said that he was not, almost certainly believing that they were replying not as ordinary voters, but as scientists with access to sources of knowledge unavailable to the hoi polloi. Goldwater sued the magazine for defamation, and won, after which the American Psychiatric Association laid down a rule that said, It is unethical for a psychiatrist to offer a professional opinion unless he or she has conducted an examination and has been granted proper authorization for such a treatment.

　　Inadvertently, the psychiatrists demonstrated how difficult it is in this field to separate technical judgment from moral judgment.

　　Whether this was a counsel of perfection or a limitation of freedom of opinion, or both, has been debated ever since. It might be that a psychiatrist has a right to express an opinion as a private citizen, as has everyone else, about a politician’s mental fitness for office, but not qua psychiatrist, thereby claiming special authority. This seems to me sophistical, however, arguing for a distinction without a difference.

　　In 2017, Dr. Bandy Lee, a psychiatrist at Yale, edited and published a book of essays by mental health clinicians claiming that Donald Trump was not mentally fit to be president, and would be dangerous as such, opinions allegedly based upon some technical knowledge that they, the authors, had that was not available to mere laymen.

　　In essence, their claim was that President Trump had, or suffered from, a personality disorder, or several personality disorders, and that his conduct consequent upon this disorder, or these disorders, rendered him unfit for office. 

　　They diagnosed the personality disorder, or disorders, by his past conduct, and because leopards do not change their spots, expected his conduct to remain the same. The logic went as follows: We know he has a disorder because of the way he behaves, and he behaves the way that he does because he has a disorder.

　　It is obvious that this offers no fresh illumination to anyone who has simply observed President Trump and come to a conclusion about his character. Some may like that character, and some may detest it. Some may detest it and yet say they nevertheless want him as president. But it is clear that we have returned to the medicine that Molière satirised in the seventeenth century: in the Imaginary Invalid, the doctor explains the tendency of opium to cause sleepiness because it contains a dormitive substance.

　　That Dr. Lee was motivated principally by political passion is suggested by the fact that she made no comment in the following years on then-President Joe Biden’s mental state. It is not this, however, that made her opinions wrong: it was their emptiness posing as technical sophistication.

　　There was recently an article in the British Medical Journal about the ethics of diagnosing President Trump’s psychological or medical condition by doctors who had never examined him. It was generally a very fair article by authors who almost certainly detested him. But while they acknowledged that his psychological or medical condition was a matter of importance, they urged caution (not quite the same as absolute prohibition) against diagnosis at a distance. 

　　And with good reason. Inadvertently, they demonstrated how difficult it is in this field to separate technical judgment from moral judgment. They wrote:

　　 In 2017, a group of mental health clinicians … accused Donald Trump, President of the United States, of being paranoid and delusional and having malignant narcissism.

　　The giveaway word is accused: a word that one does not usually employ in making a diagnosis. It implies fault or blame, a moral failing rather than a merely physiological deficit. 

　　As Hume said, reason is the slave of the passions.