For months now, ordinary people, politicians and pundits have speculated in public and private: is there, you know, something wrong with Donald Trump? Laymen would say he is “nuts” or “crazy”, while a mental health professional might say “suffering from a personality disorder”.

It’s not one trait or attribute, but the whole complex of behaviours: lack of impulse control, self-obsession (to the point at which all human tragedies are seen as they affect him — the Orlando massacre proves was he right! Nykea Aldridge was killed, so vote for him!), habitual lying and exaggeration, grandiosity, lack of empathy and need for constant adoration. There is also his rambling, sometimes unintelligible speech pattern. He flits from one thought to the next by stringing sentence fragments together, never completing a thought or a sentence.

We have seen TV diagnoses, most recently from David Plouffe (“psychopath”) and Monday from the Morning Joe panel. Such pronouncements are met with the admonition that it is inappropriate and impossible to diagnose mental illness without examining the patient. But, of course, we are in an election, not a hospital; talking heads are not bound by the limits of medical ethics. Besides, what if he really is suffering from some mental illness?

There are several considerations at work here. First, the answer to whether he is mentally ill is unknowable, because Trump is not about to admit he has a problem, nor submit to an evaluation. (If he did, the ensuing report would no doubt be written in Trump-ese, like his first doctor’s note. The most awesome mental health of any president ever!)

Second, the conversation is unproductive, since it inevitably comes down to the debate not about Trump but about the impropriety of rendering medical judgments from afar. Third, it leaves open the door to scurrilous accusations from Trump and his minions that Hillary Clinton is seriously ill, an accusation entirely without foundation.

Most important, however, it does not matter. We don’t care, and it should not matter, if Trump has “narcissistic personality disorder” or is just a self-centered jerk. Whether he is ill or evil, afflicted or just obnoxious, ailing or inhumane, the result is the same.

At age 70, he is not about to “seek help” or change his behaviour. He may be unable to change his behaviour; he certainly is unwilling to. Whatever the origins of his behaviour, the results — millions of Americans are concluding — make him unfit to serve.

Presidents need to read and learn from others; Trump consults his “own brain”, seems to read nothing longer than a National Enquirer article and says he only surrounds himself with people who are not as smart as him. Presidents need empathy; Trump has none. Presidents must be calm under stress, exercise self-control, and be precise and measured in their responses to events. Trump flails wildly, becomes more erratic under pressure and routinely reacts out of anger. Presidents are entrusted with great power; Trump abuses his position (for example, forcing others to sue him to get paid) and is devoid of respect for fellow human beings. We ask presidents to be role models; Trump is vulgar, crude and materialistic, reducing the world to winners and losers.

It might be reassuring in some sense to find out that Trump is ill. The reality is that it’s just as likely that he’s an obnoxious, entitled ignoramus. Either way, he shouldn’t get anywhere near the Oval Office.

• Jennifer Rubin writes for The Washington Post.