With what Graham Richardson used to call “the free personality analysis” — by his account, he and Paul Keating performed one on each other at the end of their long political association — Brendan Nelson left politics, describing his successor as suffering from “narcissistic personality disorder”, which had the press, and almost certainly Turnbull’s gormless advisers, reaching for the Google.

The line gained a whole news cycle of coverage. It didn’t deserve it, and the parting shot discredits Nelson not only as a failed politician, but also as a medical professional. It does nothing but add to the junk of our political culture.

What is this strange concept of “personality disorder”? It is a fairly recent category in psychiatry, used to replace a series of alleged mental conditions — hysteria, neurosis — which had developed from the birth of psychiatry and psychoanalysis in the late 19th century. The various set of PDs — borderline, narcissistic, passive aggressive, oppositional defiant, anti-social, etc — overlap to some degree.

But they have two things in common: first, the sufferer is what we would call in common parlance, well fucked up. They all have some basic set of misunderstandings — so deep as to be relatively impervious to reflection and change — about the boundaries of self, cause and effect, their relationship to other people. Secondly, the condition is so bad that it is disabling, making it difficult to pursue careers, hold relationships, friendships, etc.

The latter qualification is important, because it only really qualifies as a PD condition if someone’s life is lying in pieces on the floor. The idea of PDs has gained a lot of criticism of late — especially the way in which new ones are budded off at the drop of a hat by the editors of the DSM, the Diagnostic and Statistical Manual for US psychiatrists. The original purpose of the DSM was to try and develop standard classifications so that psychiatrists from different schools of thought could talk to each other.

In the huge hospital of America, it now has another purpose — to make the treatment of mental health quantifiable for insurance companies. But like ADD and bipolar disorder (manic depression) it has spread from the small number of people genuinely suffering something major, to the cause of social control of youth (in the case of ADD), and avoiding dealing with one’s deep internal conflicts by self-diagnosing (bipolar disorder).

Now whatever else Turnbull is, he is not ineffective in his life. He has a long-standing marriage, a successful legal and business career and appears to have more friendships than your average pollie. By definition he is an ordered and integrated subject.

Quite possibly he is also an a-sehole — rude, arrogant, individualistic, backstabbing without compunction. But, of course, Nelson couldn’t say that as the door hit him on the way out, because that would be a pure cry of pain, an admission of howling defeat. So, to try and gain a last bit of power, he resorts to professional power to try and portray Malcolm in a muddle. Good, hah? I got lots of those. Where was I?

Ah yes. There are two possibilities — either Nelson doesn’t have a clue about what a NPD description really involves, or he does, but is willing to misuse the discourse to make a cheap point. It’s pathetic and professionally disreputable.

It does, however, serve one function — to make clear how much psychiatry is about power, that of one subject, the doctor, to turn another subject, the patient, into an object by the application of a jargon. In some cases that is necessary and therapeutic as a stage in treatment of people in a severe bind. But its remorseless spread is simply an attack on the idea of the free, or potentially free, human being, shaping their own lives.

Some people sometimes lose that freedom or never gain it (most serious personality disorders result from violent childhoods or disturbed families — the personality “sets” like a permanently broken bone, another reason not to be flippant about it).

And the psychological interpretation of politicians and public figures is quite legitimate, and necessary — and if Turnbull’s colleagues had done a bit of thinking about the wellsprings of his impetuousness and short attention span, some might have had valuable second thoughts about his elevation.

But the pathologisation of the varieties of human behaviour is something else. Illiberal in the extreme, the fact that liberals seem most interested in engaging with it — Jeff Kennett, on the basis of a pamphlet someone read to him, saw fit to diagnose Mark Latham with bipolar disorder — is a measure of how degraded the tradition is within the party that bears its name.