Jordan Peterson, the Canadian professor of psychology who in the last year has become North America’s most popular public intellectual, has spent many decades studying tyranny and its antecedents. As a result, he frequently warns his audiences of the unparalleled destructive power of “ideological possession."

As someone who has long been writing about the threat posed by this all too prevalent epistemic disease, I am delighted to see the attention that is now being paid to it.

Ideological possession is to healthy political discourse as scientism is to science.

The most important thing to know about diagnosing ideological possession is that you can’t do it by looking at the content of the possessing ideology.

As I have said elsewhere, it’s not the content of your belief that makes you dangerous: it’s the way you believe it.

Any ideology has the potential to be deadly when advanced by those who are so sure of their own knowledge and moral outlook that they would impose it against the protestations of those affected by it. To the ideologically possessed, the imposition can always be justified, because “it’s the right thing to do”; “it will start working if we keep at it”; “the complaints are coming from bad people," and so on. (Yes. The logic is as circular as it seems.)

So, with apologies to Dr. Peterson and an open invitation to him to amend and augment the following (he is the clinician, after all), here for diagnostic purposes is a list of symptoms of ideological possession - that most fatal of epistemic diseases.

Symptoms & Manifestations

The symptoms of ideological possession manifest differently according to the possessing ideology.

So for illustrative purposes, the following list of symptoms is presented with example manifestations, labeled to indicate their association with so-called “progressive” (P), so-called “conservative” (C) and so-called “libertarian” (L) possessing ideologies.

To be fair, it is not the case that all people who present with manifestations similar to those listed below are exhibiting symptoms of ideological possession. It is, after all, quite possible to hold apparently simplistic or radical views that are very carefully arrived at, with an open mind, good data, and intellectual honesty.

For instance, the fact that someone believes the world is out to get them doesn’t necessarily mean they are paranoid (B does not imply P). More interestingly, as the old saw goes, just because you’re paranoid, that doesn’t mean the world isn’t out to get you (P does not imply B is false).

Nevertheless, believing the world is out to get you is a very good diagnostic marker for paranoia (B is highly causally correlated with P).

So with that caution, the manifestations below are offered because I have witnessed each one, and when I did so, had reason to believe it was symptomatic of at least the early stages of the onset of ideological possession.

List of Symptoms - for Diagnostic Purposes

Major Symptoms

• The possessed insists that anyone who disfavors a specific view or policy must also reject the basic moral value that, to the possessed individual, justifies that view or policy. (This is the fallacy of the assumed paradigm. L: “if you won’t let mothers protect their children with guns, you’re a misogynist”; C: “people who favor gun control don’t value freedom”; P: “people against regulating firearms don’t care about violence against children”.)
• The possessed uses one-dimensional labels for people they’ve never met (and who clearly aren’t one-dimensional) as a means of dismissing the value of all their beliefs or actions. (L: “Churchill was a mass-murderer”. C: “Ghandi was a pedophile”. P: “Thatcher was a witch”.)
• Related to the above, the possessed will regard a few quotes or actions of an individual as proof that the individual is evil without regard to context, appreciation that everyone is a product of his time, recognition that people change over time, or consideration of other quotes and actions that provide evidence against the claimed ill intent of the individual in question.
• The possessed advocates worse treatment of people within a specified group worse than others. (P: “Straight white men have privilege and so should have their opinions discounted or suppressed”; L; “people who work for the state initiate violence, and it is ok to use violence against those who initiate violence”; C: “people who burn the flag are traitors and should be punished as such”.)
• The possessed believes that a single principle provides answers to most important moral and political questions, disregarding reasonable moral intuitions to the contrary (precisely because they are to the contrary) and any uncertainty regarding the precise meaning or application of the principle. (P: “equality”, L: “non-aggression”, C: “Biblical authority”)
• When the results of an ideologically justified action are the opposite of those intended or used to justify that action in the first place, the possessed is convinced that not only is the action not the cause of any resulting problem, but that more of the same action will eventually solve that problem. (P: “Venezuela needs more socialism”; C: “we need more unprovoked military involvement in conflicts that don’t involve us; L: “Europe should open its borders immediately to everyone”.)

Minor Symptoms

• The possessed enjoys opportunities to defend what he believes more than opportunities to make his beliefs more accurate.
• The possessed collects data that support her beliefs instead of seeking data that would help her correct false beliefs.
• The possessed offers unsolicited opinions without any empathic engagement with the recipient or any interest in whether she is in any state to be positively influenced by them.
• The possessed would rather reform society’s institutions to better serve his ideology than reform his ideology to better serve people.

Immunity, Pathology, and Cure

Fortunately, the epistemic immune system of most mentally healthy people protects them from ideological possession. The core of the immune response – and indeed an effective cure - is Love of Truth, and specifically the holding of Truth as the highest moral value.

Pathologically, ideological possession may even be understood as the substitution of that highest value by another.

Love of Truth in fact provides a near-perfect protection against ideological possession because the disease, while deadly, has no defense against the honest admission by the afflicted of his or her symptoms.

Nevertheless, the most pernicious and subtle feature of the disease prevents the possessed from seeking treatment or treating himself: ideological possession can disguise itself in the mind of the afflicted as that very same Love of Truth that, in its authentic form, would cure it.

What conditions, then, enable those in the grip of ideological possession - whose love of Truth may have already been replaced by a counterfeit - to cure themselves?

To answer that, it is important to understand the symbiotic relationship of the disease with its host.

Although epidemics of ideological possession can be fatal to entire societies, the disease provides immediate benefits to the individual who is afflicted, such as intellectual certainty and stability, feelings of moral superiority, an apparent simplification of life’s difficult decisions and questions, avoidance of true moral responsibility, and a sense of belonging among others similarly afflicted. All of these tend to prevent self-treatment.

Accordingly, the cures for ideological possession tend to be external and unsought. They nevertheless exist and fall into two broad categories – fast cures and slow cures.

Fast cures tend to be triggered by a catastrophic failure of one or more of the above benefits to the afflicted individual. This may occur when, despite the highly motivated perception and reasoning of the possessed individual, she experiences an unexpected, painful and shocking outcome of an ideologically motivated action. The painful shock activates the Love of Truth for long enough to locate the cause of the pain, forcing the afflicted to admit the symptoms, and therefore identify the disease for what it is, effecting the rapid cure.

Slow cures tend to involve a rising awareness by one afflicted individual of the same disease in friends or others with whom she identifies. This can be induced when the individual sees inconsistencies in those others’ words and actions that cause direct harm to others and to the stated goals of the possessing ideology. (In theory, this slow cure could be induced by observations of one’s own actions under ideological possession, but this is prevented by the self-righteousness that is felt when one acts in the grip of the disease.)

Maintaining Good Epistemic Health

To protect oneself from the terrible epistemic disease of ideological possession, epistemic nutrition and exercise are extremely effective.

With respect to the former, the regular consumption of great thinkers like JS Mill (“He who knows only his own side of the case knows little of that”), George Orwell (“To see what is in front of one’s nose needs a constant struggle” and Dostoevsky (“Nothing is easier than to denounce the evildoer. Nothing is more difficult than to understand him”) will keep you in good epistemic health. Supplement these basics with a more varied diet of thinkers with whom you disagree on things that matter, and you’ll be in even better shape.

With respect to the latter, a comfortable regime of epistemic exercise - which takes a little time and effort but is immediately rewarding - involves maintaining real friendships with people who have very different assumptions, experiences and declared moral and political priorities from your own.

The good news is, if you’re chasing Truth hard enough, it is very unlikely that this particular disease will ever catch up with you.

Robin Koerner is a political and economic commentator for the Huffington Post, Independent Voter Network, and other outlets. He holds graduate degrees in both Physics and the Philosophy of Science from the University of Cambridge (U.K.). He is British born, and recently became a citizen of the USA. A decade ago, he founded WatchingAmerica.com, an organization of over 200 volunteers that translates and posts in English views about the USA from all over the world.