This behavior may be evidence of some underlying disorder, or it may not. Who knows? Mr. Trump hasn’t undergone a mental-health evaluation, at least not one made public. But even if his behavior were diagnosed as an illness, what would that tell us that we don’t already know? Plenty of people with mental disorders or disabilities function at high levels of society. Conversely, if Mr. Trump were found to have no diagnosable illness, he would be no more fit for the office he holds than he is today.

The problem lies in trying to locate the essence of Mr. Trump’s unfitness in the unknowable reaches of his mind, as opposed to where we can all openly see it and address it in political terms. As the psychiatrist Allen Frances told The Times: “You can’t say enough about how incompetent and unqualified he is to be leader of the free world. But that does not make him mentally ill.”

Unfortunately, a number of psychiatrists, politicians and others who should know better have increasingly taken up the Trump-is-crazy line. In “The Dangerous Case of Donald Trump,” released last October, more than two dozen contributors, most mental-health professionals, concluded that Mr. Trump presents a grave and immediate danger to the safety of America and the world. No argument there, but why do we need to hear it from psychiatrists relying on their professional credentials? Dr. Bandy Lee, one of the book’s editors, said the authors are “assessing dangerousness, not making a diagnosis.” Anyone with access to newspapers or Mr. Trump’s Twitter feed can do the same.

The psychiatrists say they have a duty to warn the public about what they see as a serious threat to the nation. That’s commendable, but they should consider how their comments will be taken by the vast majority of Americans, particularly in a highly politically polarized time. The language of mental health and illness is widely used yet poorly understood, and it comes loaded with unwarranted assumptions and harmful stereotypes. There’s a good reason the profession established an ethical guideline in 1973, known as the Goldwater Rule, that prohibits psychiatrists from offering professional judgment on public figures they have not personally examined.