There is a virulent form of unpatriotism festering in America today. Like an algae bloom that deprives life of oxygen, it starves democracy of the air of reason. It now thrives on what we call the far left, but like a dead zone off the coast, it moves with the tides.

I am referring to the seditious dementia of conspiracy theories, the death of faith not in some mere administration or Congress but in America itself.

Haven’t you heard? The U.S. government blew up the World Trade Center. Oh, sorry, that’s not right. The planes did knock down those buildings, but the White House was in on it. Oh, no, sorry again, that’s not what happened. It was the Jews. They razed it without leaving any fingerprints — save for the 4,000 Zionist co-conspirators who were tipped off in advance — in order to frame the peace-loving Muslims of al-Qaida. (Those crafty Hebrews are always coming up with clever ways to make Islamic fanatics look bad, like getting blown up.) Bin Laden’s admission that he did it? Well, of course. He’s in on it.

Presumably, Bush’s demolition experts applied the same expertise to the levees in New Orleans. That’s another theory in wide circulation today thanks in no small part to Spike Lee, who gave it a fair airing in an HBO documentary.

The metaphysical, ontological stupidity of all this defies rational rebuttal. It would be like proving I didn’t have unicorn for dinner in late December of 1987.

Here’s a question: How is a president willing — and able! — to bring down the World Trade Center, murdering nearly 3,000 Americans without inspiring a single whistle-blower or attracting a solitary eyewitness, somehow morally or logistically incapable of planting some exculpatory WMDs in Iraq?

As for Spike & Co., what took Bush so long? Why wait for a hurricane? Oh, how he must have yearned, his men and equipment long in place, to cleanse America of the Big Easy. Oh joyous St. Katrina’s Day! And yet, Bush failed to plan for the aftermath in a way that wouldn’t defenestrate his poll numbers.

Stupidity isn’t the right word for these dark imaginings, because some of these conspiracy theorists are very smart people. Nor is it fair to say they are all left-wingers. Indeed, two prominent 9/11 conspiracy theorists — Morgan Reynolds and Paul Craig Roberts — worked in Republican administrations and have strong conservative credentials. And let us not forget that in the 1990s, sweaty fingers pointed right-to-left. Under Clinton, it was the United Nations — with its satellite office at the Rose Law Firm — that imposed order with its fleet of black helicopters.

“Conspiracy theorist” isn’t quite right either. These are priests of the Church of Conspiracy, a heresy of Gnostic heresy which holds that man is the ruler of history, the demiurge of all events that befall us. Powerful and unseen forces lurk in the shadows. The conspiracy theorists know they’re out there, even as the enemy’s name changes almost daily: Big Oil, capitalists, Republicans, or perhaps those eternal pullers of mankind’s puppet strings, the Jews.

The masons of dementia build upon a bedrock of one absolute truth: Bad things happen, and someone must be responsible. Upon this bedrock they pile convenient and selective facts like bricks. Contradictory facts are clever lies. When Popular Mechanics debunked 9/11 hokum, the immediate response from conspiratorialists was “cover-up!” and “CIA front!” because in this perverted faith, denying the ultimate truth must be proof of a lie.

This rough beast slouches toward sedition because it assumes not that our leaders are knaves or even mere criminals, but that they are murderous Supermen with no loyalty to nation, decency or law. Our Constitution is a fraud, a charade for the rubes some of us naively call citizens. If you disagree, you’re either fool or “in on it.” In his 1964 essay, “The Paranoid Style in American Politics,” Richard Hofstadter demonstrated that this fever of the mind is as old as America itself and its outbreaks flare up across the ideological landscape. What is so sad and frightening is that this diseased thinking is reaching epidemic proportions. More than a third of Americans believe the U.S. government was likely to have been involved in 9/11.

In the past, when these outbreaks occurred on the political right, liberal hand-wringers fretted about incipient fascism and rising McCarthyism. Today, the best we get from them is a bemused and sterile chuckle.