The difficulty of conspiracy thinking is its pathological character; the problem of conspiracy thinking is the enormous danger of false positives. One way to identify and challenge conspiracy thinking is to evaluate its internal coherence: 'Do these claims even make sense in their own terms?'
I previously discussed the importance of an authoritative common sense about the way-the-world-works in protecting societies from conspiracy thinking. One might call this the 'external coherence' test: are such theories consistent with what you know of how the world works? Think of Barney Frank's response to the loonies: 'On what planet do you spend most of your time?'.
I now see that distinguishing conspiracy thinking (alien abductions, the Birther movement, The Protocols of Zion, etc) from conspiracy detection (e.g. The Protocols of Zion fraud) must also rely on some elementary evaluation of internal coherence: 'Do these claims even make sense in their own terms?'
The difficulty of conspiracy thinking is its pathological character: one can never disprove a conspiracy theory even if it is plainly wrong. The problem of conspiracy thinking relates to the enormous danger of false positives. For example, the 'Protocols of Zion', purporting to describe a Jewish conspiracy to take over the world, was (and in places still is) widely believed and seems to bear at least some responsibility for the various more or less systematic and horrible attacks on Jews at various times and places in the 20th Century. It may be even be partly responsible for the tacit antagonism towards Jews which continues to this day (25% of Americans in one recent survey believed that Jews were responsible for the financial crisis). The evil that can be caused by conspiracy thinking - in its eagerness to embrace false conspiracy theories - is clear from history.
This calls for two things. Firstly we need a bullshit detector to identify the cases, and sometimes the people, one should avoid taking at all seriously, while bearing in mind that there can be real and nasty conspiracies, sometimes reaching all the way to the tops of governments (Rwanda, Watergate, Suez, etc). Conspiracy thinkers typically assert that all they are doing is following a skeptical stance to received information. In fact what they are following is a radical epistemic stance of 'possibilism' - anything that is possible deserves equal status and consideration as knowledge. This position completely rejects a central foundation of successful civilisation: the project of cumulatively and collectively enhancing our understanding of how the world works. They ask, 'How do you know the Jews/Free Masons/French government aren't behind this [unusual world event]?' They say, 'It is up to the Official Story to prove itself by disproving every other possibility'. In fact it is the skeptic who has the burden of proving the plausibility of her critique.
Secondly we need to stand up to the nonsense propagated by conspiracy thinkers. What they are doing is not harmless. It is drivel but it is dangerous drivel that can kill people directly, and also crowd out the rational debate that grown-up democratic politics depends on.
Since conspiracy theorists often claim that the world actually works quite differently than our common sense tells us, discrepancies there don't necessarily provide a simple way to distinguish bullshit. Internal coherence is therefore a useful independent test since, in principle, it can be used to assess the 1st order sensibleness of a claim even under the charitable assumption that the world really is like that. In principle this should also provide an alternative route to criticising conspiracy claims in terms the conspiracy thinkers themselves might accept, since the problem is not that they are stupid, but that they come to foolish conclusions.
"Marxism, Conspiracy, and 9–11" by David MacGregor and Paul Zarembka*
I recently came across this somewhat typical example of conspiracy thinking, unusual only in being published in a peer-reviewed academic journal (what kind of peers, one wonders). The authors claim that, as Marxism has revealed, the grand bourgeoisie are constantly engaged in conspiracies inside and outside of government to further their capitalist interests through "bourgeois terror", such as the US domestic conspiracy to simulate an external attack on the World Trade Centre as an excuse for a profitable war with Iraq. They discuss some grey literature (mainly internet self-published) 'researching' the evidence against the Official Story of 9/11 and assert that a US government-capitalist cabal conspiracy must be the real explanation. The particular claims here are integrated into a Marxist world-view that is clearly compatible with bizarre and massive government-capitalist conspiracy (if not dependent on it), so criticising this conspiracy's external coherence with the way the world really works is not promising. In fact it's the very argument, and attention, these people are dying to get.
But fortunately it's not necessary to even look at external coherence when the internal coherence is so bad. These are basic errors of reasoning at various levels which I think apply to most conspiracy thinking.
1. Problems in the evidence for the Official Story are not evidence for the conspiracy theory
The level of scrutiny brought to the Official Story is not replicated for the conspiracy version. In this case the official 9/11 story is examined minutely for any minor inconsistency - the melting points of structural beams, and so on (this seems a common theme - Jewish holocaust 'truthers' frequently go into great detail about the amount of rebar in the concrete ruins of alleged gas chambers). Any such inconsistency is taken to be definitive evidence of conspiracy.
On the one hand there is an explicit commitment to extreme skepticism in that Type 1 errors (believing something which is actually false) must be resisted at all costs. On the other hand this skepticism is only applied to the Official Story. The alternative conspiracy story is assessed under a quite different, though implicit, commitment to avoiding Type 2 errors (missing what is really there) at all costs. This can fairly be described as a commitment to extreme gullibility.
The result is the logical equivalent of claiming that evolution has some missing links and therefore Intelligent Design is true.
2. The possession of a microscope does not make you a scientist
Although the Official Story is analysed as if it is 'just a theory', with full 'scientific rigour', this is not backed up by anything resembling a scientific attitude but rather a self-serving pedantry. Rigour for the conspiracy theorist means pointing a microscope at certain arbitrary places, rather than any kind of systematic and comprehensive analysis. (This lack of perspective characterises most amateur research - whether 'investigating' climate change theory or criticising research on inequality - although that doesn't necessarily invalidate it.) There is little ability or interest for impartially assessing the quality of sources: any old crap on the internet that fits your view is taken on faith; the findings of Official Story institutions are pre-refuted.
This is a mockery of honest research and reflects a basic misunderstanding of scientific method. Scientists are not only non-conformist sceptics looking to poke holes in conventional wisdom (trying to disprove the hypothesis). They also take responsibility for constructing robust and complete alternative theories that can do a better job of accounting for the evidence in an objective comparative assessment. Scientific scrutiny has a special epistemic status because it strives to be constructive, impartial, and open-minded (though disciplined), but conspiracy thinking is characterised by its closed-minded dedication to the truth it already knows, almost visceral distrust of the Official Story, and a search for the right evidence (that supports its view).
3. A house-of-cards
The extravagant claims of a conspiracy theory have a certain plausibility considered individually and in an ad hoc way. I mean that they seem possible, not necessarily probable, either in the sense of being probe-able (withstanding rigorous scrutiny) or at all likely. This is the nature of possibilism. But on closer inspection, when one tries to take them seriously as a positive coherent account, they have gaping logical flaws.
Like, why pretend Osama and a bunch of Saudis did 9/11 if your plan is to justify invading Iraq? If you're so smart and powerful, why would you have to start a war to make money? Why make it so complicated that so many things could so easily go wrong?
Focussing on particular claims does no better. Why make up a list of fake hijackers using the real names of living people who are left around for journalists to find? Why do something so terribly difficult, risky, and expensive, and then short airline stock? Why plan to blow up 3 WTC buildings but only fly 2 planes into them - what kind of math skills are these all-powerful cabalists supposed to have?
When challenged, conspiracists will always find further ad hoc answers that cover the gaps, but their account grows ever more absurd, unlikely, and contradictory the more you try to fit its pieces together, which is rather the opposite of what one expects of truth. It has a conjunction problem in that when you try to combine the possibilities of each claim the combination quickly becomes wildly implausible. (See here for a good example of such analysis from Mitchell and Webb.)
4. All narrative and no plot
Conspiracy theorists appear to offer so much, but actually fail to say anything very precise at all about what is really going on. In particular, they usually fail to provide a specific account of any of the basic plot elements - the crime, criminal, and motive - and the relationships between them. The conspiracy narrative comes first, and motivates a search for the plot - one must take it on faith that it is there. Usually we get a very blurry account of any of it. E.g. for 9/11
The crime itself: faking a terrorist attack and killing thousands of Americans. That's not very precise is it. This was a conspiracy involving presumably thousands of people, dozens of government agencies, clockwork precision. Can't you say anything more about how it really happened? Nope.
The criminals: The US government and an (international) capitalist cabal. Apart from Bush and Cheney (naming whom is more of an autonomic reflex than a thought process) can you name anyone who was involved? What, not even one low or medium level conspirator?
The motive: capitalist profit, by manipulating a country into war. Certain special people manage to be quite sure of seeing directly to the heart of the truth by looking very hard at the internet and asking themselves that sophisticated non-conformist question: Cui bono? (Who benefits?). But other investigators rarely come to the same conclusion. Nor does it seem a very intelligent starting point in an investigation to assume we are in an Agatha Christie detective novel. After all, cui bono can be asked about Icelandic volcano activity, or World Cup results. Or global climate change theory: those evil science professors are after power and money! or maybe its the Chinese trying to sabotage our economy? or maybe its United-Nations-socialists trying to take over the government and destroy the American way of life? or maybe.....
Indeed cui bono? can be asked of conspiracy theorists themselves. Frankly I'm not surprised to see Marxists publishing this - they'll say anything to get some attention? See how easy it is? Actually in this case I think it must be true, since it rather suits the point I'm trying to make.
Conspiracy thinkers often assert that what they do is necessary, because there are real and terrible conspiracies in the world that would otherwise go undetected. But the trouble is that what conspiracy thinkers produce is so totally nebulous or, where precise, usually demonstrably dead wrong, that they give us no guidance for detecting actual conspiracies! I dispute that we need conspiracy thinking to protect us from real conspiracies. One is reminded of all those heterodox economists who claimed to have predicted the 2007 credit crisis. On looking more closely, they were just saying the same things they always say - 'this neo-liberal economy is unsustainable' - but that is not the same thing as successfully predicting the particular form and course of this particular crisis. Even a broken clock will show the correct time twice a day, but that doesn't mean it is ever right, or helpful.
5. Privileged observer status
This doesn't apply to all conspiracy theorists to the same degree, but many seem to forget that if there really is a gigantic evil conspiracy, it would be out to get them too. MacGregor and Zarembka for example claim to believe that their own government committed mass-murder (9/11) in order to further its agenda of more profitable mass-murder (Afghanistan & Iraq). And yet they dared to publish the truth? Do they think tenure will protect them? I'm sure they're not stupid, but the remaining options are that they are suicidal; know that no-one will ever take them seriously; or know deep down that this is bullshit. Their own actions seem in conflict with their thesis.
Unfortunately although this article is published in a Marxist journal it is run by fiendish capitalists who would like to charge you $30 for the privilege of reading it. Which is a shame since the full article is so hilarious that before writing this I needed to check with the editor that it wasn't a spoof. He then called me "ideological". Priceless!