In the US we are living through a heyday of conspiratorial nonsense, most dramatically the deranged QAnon cult that surveys suggest is, at least in part, believed in by many Republicans, including some members of Congress.
Beyond these fringes, though they are hardly as fringe as they once were, both left and right have developed widely accepted paranoid theories that profoundly misrepresent how politics and policymaking actually work, and badly damage the national conversation.
Most of the right appears convinced that there exists a nefarious cabal of administrators, bureaucrats and others in government plotting against conservatives, especially former president Donald Trump, and enforcing an insidious far-left agenda. They call this the "deep state," conjuring up images of a permanent administrative establishment manipulating and bypassing political leaders, as military and intelligence officials allegedly historically did in countries like Turkey, where the term “deep state” was coined, and Pakistan.
The fantasy is used to explain policy failures and blunders by political leaders such as Mr Trump and his allies, or as an explanation for why experts and officials contradicted their more bizarre pronouncements.
Criminal prosecutions of many of Mr Trump's associates, including former national security advisor Michael Flynn, former campaign chairman and White House strategist Steve Bannon, former campaign manager Paul Manafort, and many others are chalked up to machinations of the deep state.
So is Mr Trump’s defeat in the 2020 presidential election, which many Republicans believe was stolen through fraud by the deep state, even though the election was remarkably clean and well-run despite the pandemic.
The deep state is also blamed for the pandemic itself, for the economic collapse it produced, and for supposedly lying to Americans about everything from mask-wearing to vaccines.
This extreme and widespread paranoia is largely responsible for the fact that even though Covid-19 vaccines have been easily available to adult Americans for over six months, about a third of the population, largely in Republican-leaning states, remain unvaccinated and bitterly reject masking and other crucial mitigation practices.
Instead of pride in one of the few countries where vaccines are readily available, and gratitude to the administrators who organised it in remarkably short order, much of the right rages against the Centres for Disease Control and Dr Anthony Fauci, chief medical adviser to President Joe Biden. He is routinely depicted as a nefarious leader of the deep state, and has been disparaged by Republican leaders like Florida Governor Ron DeSantis, who is, not coincidentally, now presiding over one of the worst outbreaks of coronavirus in the world.
There is, of course, no American deep state.
There is a US government, with officials and administrators. But there is no cabal, no plot and no parallel authority. That is a fantasy, but also a useful, albeit absurd, explanation that exculpates right-wing heroes like Mr Trump and places all blame on a shadowy group of liberal plotters supposedly controlled by the likes of Dr Fauci.
This position reflects a generalised animosity towards expertise that permeates the populist right, especially in western countries, where conservatives now consider knowledge and experience to be a black mark against any official, scientist or analyst.
This same antipathy towards expertise and knowledge is expressed, in an only somewhat different form, in the liberal version of grand conspiracy theorising: the mirage of the "blob".
A number of former officials from the Barack Obama administration, most notably former speechwriter Ben Rhodes, deride the foreign policy establishment as a monolithic and homogenously hawkish cult that invariably pushes in lockstep for military action.
That is supposed to explain how the US ended up in protracted wars in Afghanistan and Iraq, with troops in Syria, and other military commitments around the world, on top of a history of other military actions.
The fantasy of the blob is primarily employed by isolationists as a rhetorical tool to bolster their case by pretending they are bravely confronting a uniformly militaristic and interventionist opposition that is institutionalised and exceptionally difficult to overcome.
But, as in the case of the deep state, the blob plainly does not exist.
In fact, the “foreign policy establishment” and the analytical policy-framing community is decidedly heterogeneous, particularly compared with the second half of the 20th century, when there was a broad consensus about the Cold War.
In recent decades, by contrast, influential and respected policy analysts, and former and even current officials, in and during all recent administrations held a wide range of attitudes on when and how to use military power, what the global force posture should look like, and especially what the major US strategic goals are and how they should be achieved.
Unanimity is the one thing you almost never see.
But it is much easier for those who find themselves repeatedly on the losing side of arguments, largely because they are making bad cases for bad policies, to chalk everything up to a nefarious cabal on the other side.
Just as much of the right fantasises that a non-existent liberal deep state manipulates domestic policy, many on the left now believe that an equally chimerical right-wing, or at least hawkish, blob dictates most foreign policy.
In both cases it is absolute nonsense but also extremely convenient and deeply reassuring.
The prevalence of such paranoid phantasms infiltrating both Republican and Democratic mainstreams is extremely troubling.
Clearly there is no deep state and no blob. But in both cases the willingness to seek refuge, reassurance and emotional comfort in patent hallucinations – both rooted in antipathy towards expertise and experience – demonstrates a deeply disturbing collapse of confidence in competence.
That is, of course, not completely baseless.
The CDC made mistakes during the coronavirus pandemic, but it has been dealing with an unknown disease. The US government has made terrible foreign policy mistakes in recent decades, but many experts and officials warned against them, and virtually none were uniformly supported by any means.
Cynicism and misgiving are understandable affects, and scepticism is a healthy political impulse. But this degree of alienation from a fine cadre of public servants and other experts genuinely dedicated to serving the country is deeply damaging.
More significantly, the US political process cannot be relied on to make rational policy decisions until these demons of deep-seated doubt are finally exorcised.