When it comes to such things as whether or not the US administration was behind the 9/11 attacks, if there is a global Zionist conspiracy, whether the moon landings were faked or not, and so on, then there exist objective truths of the matter. If we were in full possession of all the relevant facts, and were cognitively accurate in our analysis of these facts, then we would have no doubt as to what these truths are. The problem arises because we usually don’t have access to all of the relevant facts, and our analysis of the facts that we do have can err in a number of ways. Nevertheless, there are still better and worse ways of getting to the truth.
If we wish to form warranted beliefs about these and other matters, then we first need to establish as many well-grounded and relevant facts as possible, and then use a good method to form our beliefs based upon these facts. To be deemed a good method, it should exhibit predictive success (which is what we really mean by something being true), and convergent accumulation of consistent results. That is, we should expect it to routinely produce propositions that have predictions that match reality, and continue to do so if we investigate them from different angles. The methods of reason and science have proven to be the preeminent methods for learning about the world.
Conversely, if we start with few well-grounded facts, or supposed facts that are actually false, and then use a poor method in order to form our beliefs from these facts, then our beliefs will likely be false. In the worst case, if we form our beliefs based upon nothing more than hearsay, desire, and speculation, then they are almost guaranteed to be false. The reasons for this are firstly that false beliefs are just as easily propagated as true ones; and secondly that the number of false beliefs will always vastly outnumber the number of true ones, so any arbitrarily chosen belief that is not well-founded (i.e. not based upon evidence and reason) will almost certainly be false. Based upon these thoughts, here are a number of ways in which conspiracy theories go wrong:
1. They get their facts wrong
If we start with incorrect facts, then any conclusions deduced or inferred from these ‘facts’ will be unwarranted. For example, some 9/11 conspiracy theorists believe it is a fact that mobile phones do not work in airborne planes, and then deduce from this ‘fact’ that the phone calls from the passengers and crew aboard the hijacked planes must have been faked. However, some of the calls made from the hijacked planes were made from air phones, not mobiles, so the objection is immaterial in that case. Moreover, it is not actually true that mobiles don’t work at all in planes that are airborne. A mobile phone will in fact often work when a plane is closer to the ground during the climb and the descent, and even sometimes when the plane is at cruising altitude if it is flying in the vicinity of a strong signal from a phone mast.
Another example of a mistaken fact is that the explosion in one of the tube trains on 7/7 came from underneath the floor – suggesting that a bomb had been planted there earlier (as part of a conspiracy by the government/security services, we are supposed to infer). However, this ‘fact’ is also incorrect. It came originally from an early report from one eyewitness aboard the tube train in question, and was then widely disseminated on the internet. However, later eyewitness reports – including those from passengers who were much closer to the explosion – made it clear that the source of the explosion was the terrorist’s backpack, and not somewhere underneath the train.
An oft-repeated claim made by 9/11 conspiracy theorists is that around 4000 Jews stayed away from work at the World Trade Centers on September 11th. However, this ‘fact’ is also false. Estimates from the 1700 dead based upon the religion listed put the number of Jewish at 270. Another estimate based the last name of victims put the total number of Jews at up to 400. A survey of 390 victims who worked for Cantor Fitzgerald found that 49 were Jewish. This accords well with New York State’s population in general, in which 9% are Jewish.
Fake Moon landing conspiracy theorists point to many supposed impossibilities or inconsistencies with the evidence. One of these is the ‘fact’ that a flag cannot wave in a vacuum, but that the American flag was seen to wave in the film footage from the Moon. However, in one photo that is often cited, the flag is ‘waving’ because the pole to which it is attached is being rotated by the astronaut. The fact that there is no atmosphere is irrelevant in this case. In other cases, the flag gives the appearance in photos of waving because the horizontal rod from which it is deployed was not fully extended, so the flag was not fully unfurled. Much more about this here: http://www.badastronomy.com/bad/tv/foxapollo.html.
There are innumerable other examples where conspiracy theorists have failed to get important facts correct. Of course, they could assert that their facts are correct, and that the generally accepted facts of the matter are actually all part of the conspiracy. However, they would further sacrifice the plausibility and parsimony of their theory if they were to take this approach. For more on this, see below.
2. They make errors of reasoning
One very prominent error of reasoning that usually features in conspiracy theories is a form of cui bono, in that they look for who might benefit from the conspiracy (often the US or other government), and then deduce that this agent is therefore responsible for the act in question. For example, 9/11 conspiracy theorists argue that the Bush administration had much to gain from perpetrating the attacks and blaming them on Al Qaeda, as this would give them an excuse to go into Iraq and Afghanistan, thereby getting rid of an uncooperative Sadam Hussein, getting control of some of the region’s oil, and distracting the electorate from other of the administration’s policy failures at home etc. However, we are not entitled to deduce logically from the existence of these benefits (even if we suppose them to be true) to the US government being responsible for the attacks. It is a logical fallacy of the form:
P1: X would benefit if event Y was to happen
P2: Event Y happened
C: Therefore, X caused event Y to happen
A simple counterexample should suffice to show the fallacy:
P1: My local pizza takeaway would benefit from a Credit Crunch (as more people would then buy pizza)
P2: The Credit Crunch happened
C: Therefore, my local pizza takeaway caused the Credit Crunch to happen
In response to this, one could argue that the US administration had the means, as well as the motive, to carry out the 9/11 attacks and then cover it up, whereas my local pizza takeaway didn't. However, as I will argue below, whether it actually had the means to do this is part of my disagreement with conspiracy theorists - so that response would beg the question. Moreover, even if we were to grant, for the sake of argument, that the agent in question has both the motive and the possible means, I can give a new counterexample as follows:
P1: John would benefit (financially) if his wife's parents were to die
P2: John's wife's parents are killed in an apparent accident
C: Therefore, John caused his wife's parents to be killed (and made it look like an accident)
Whilst it's possible that John did indeed arrange to have his wife's parents killed, the mere fact that he had both the motive and conceivable means doesn't lead to that conclusion - the argument is a non-sequitur. That he had motive and possible means might cause the police to question John, but if there was overwhelming evidence that he didn't commit any crime, then means and motive alone would carry little weight. So, we cannot legitimately deduce from identifying who would benefit from the occurrence of some event to the conclusion that the agent in question caused the event to happen (even if the agent in question might have the means to cause the event).
Some may attempt at this point to rescue the weak motive and means argument above by adding that we have prior experience of the type of agents under consideration (typically some Western government, or State or military body) carrying out similar acts, and therefore they should come under strong suspicion whenver something like this happens. However, it is precisely because we don't have any good precedents for such large-scale, audacious, and often ruthless conspiracies that they are the stuff of conspiracy theory at all (although small-scale and mundane conspiracies have been exposed many times). If they were the type of commonplace event that would lead us to rationally suspect the US administration (or whoever) when something like 9/11 happened (or whatever conspiracy theory du jour is under discussion), then their potential guilt would be discussed and investigated widely and openly, and not just confined to the conspiracy theorists on the fringe. So, even this fails.
Another reasoning error that conspiracy theorists make is that they refuse to accept any evidence that would refute their theory, but are then extremely credulous of any prima facie evidence that would be expected on their theory. In other words, they are just looking to verify their theory, and adopt totally different bars with regard to supporting and contrary evidence – with any supporting evidence being accepted almost without question, and any contrary evidence being rejected out of hand or explained away by the introduction of some ad-hoc element (e.g. that apparently contrary evidence has been planted by the conspirators etc). In addition to the problems of confirmation bias, this strategy effectively makes the conspiracy theories unfalsifiable, as no evidence whatsoever would ever be accepted as refuting them. To hold such a belief is irrational, as it could just as easily be false as true, but there would be no way for you to ever tell, as no evidence would ever convince you of its falseness. As Karl Popper said, a theory that explains everything explains nothing.
Conspiracy theorists also err by imbuing the conspirators with omnipotence and omniscience, in that they are supposed to have almost limitless knowledge and power to plan, commit, and then cover up their conspiracies. They believe this despite abundant evidence for the widespread incompetence and ignorance of government, security services, and other agencies, the general fallibility of human beings, and the fact that even small-scale conspiracies are often bungled and uncovered by the mainstream media.
Another error of reasoning that conspiracy theorists make is to argue “possibly, therefore probably”. Yes, it is possible that the US administration was behind the 9/11 attacks, that the Moon landings were faked, that the AIDS virus was created artificially in order to kill black people (or homosexuals), or even that the world is secretly run by a secret cabal of giant lizards or that the previous pope was a robot etc. However, the fact that something is theoretically possible does not mean that it is at all probable, or that it is anything like the best explanation for the facts at hand.
In general, when we are faced with multiple hypotheses that would all predict some set of observations (as we will always be in the real world), then if we are looking for the truth we need to look for the best explanation for the observations. We could test hypotheses formally using Bayes’ Theorem (http://en.wikipedia.org/wiki/Bayes%27_theorem), but, less formally we should apply abductive reasoning. This methodology (which can be demonstrated using Bayes’ Theorem to be valid), calls upon us to compare possible explanations for some set of observations by looking at their plausibility, parsimony, explanatory scope, and explanatory power. In the case of conspiracy theories, they fail primarily in terms of plausibility and parsimony.
For example, if we look at the 9/11 attacks, we are supposed to believe that there was some vast conspiracy involving the Administration, the security services, and the military. Furthermore, either the passengers on the planes were taken into hiding, or else killed. The terrorists would either have been planted, or else would be just patsies. All of the evidence pointing to Al Qaeda would have been manufactured. And with all of this, we are to believe that either the mainstream media is also involved in the conspiracy, or else that the (notoriously inept) government and its agencies managed to keep all of the incriminating evidence secret from the media. Of course, small conspiracies have come to light in the past (such as the Watergate and Contra scandals) but, despite being much less ambitious in scale, they notably were still exposed. We have no precedent for such large-scale and audacious conspiracies as would be required to fake the 9/11 attacks, or to create and release some virus and then convince health organisations, doctors, and worldwide media that it arose naturally. As such, the existence of such a conspiracy is inherently implausible (even if not actually impossible).
By contrast, we have lots of examples of terrorist attacks – including large-scale ones from Al Qaeda. Although this one was more audacious than previous ones, there is nothing inherently implausible about it, as it required nothing more than some planning and the involvement of some Muslims who were capable of learning some very rudimentary flying skills and willing to die for their beliefs. We have lots of examples of planes being hijacked, and lots of examples of Muslim fundamentalists carrying out suicide attacks – so there is lots of precedent. And, contrary to some other speculations, experts agree that only basic flying skills were required in order to fly the planes into the Towers and Pentagon. So, on balance, this explanation is far more plausible than the conspiracy alternative. Similarly, we have lots of precedent for viruses arising, mutating, and spreading naturally (just think of previous flu epidemics, for example). So, again, this is inherently more plausible than the alternative explanations. The only way around this is to presume that all of these precedents were themselves conspiracies, in which case the theories would gain plausibility at the expense of parsimony – see below.
When we examine a theory’s parsimony, we are applying Occam’s Razor (http://en.wikipedia.org/wiki/Occam%27s_razor). That is, when we have two or more theories that both predict the observations, then the simpler one is to be preferred. Or, to put it another way, we should not multiply assumptions and entities beyond necessity. For example, if we were to find a crime scene in which there was a single bullet hole in the window of house, and one bullet lying on the carpet inside, should we rather presume that just one bullet was involved, or that multiple bullets were fired through the same hole and then all but one removed from the inside of the house? Occam’s Razor would lead us to choose the former explanation, as it posits no more assumptions or entities than are needed to explain the observations. This is a good methodological rule of thumb, as it prevents us from going beyond what is supported by the evidence (and can be shown by application of Bayes’ Theorem to increase the probability that the explanation is true).
Now, in addition to their general lack of plausibility, conspiracy theories are usually for more complex and far more ad-hoc (incorporating assumptions and entities into the theories that are not themselves independently justified) than are the generally accepted explanations. Instead of just some fanatical Muslims hijacking planes and then into the Towers and the Pentagon, we have to invent some huge complex of interrelated explanations for what actually happened, how and what we were led to believe happened, and why none of this has been exposed (other than to a few diligent conspiracy theorists). Every time we think of a way that it could go wrong (eyewitnesses telling the true story, any of the hundreds or thousands of people involved could go to the press with damning evidence, or some other incontrovertible evidence coming to light), then we are forced to add some additional ad-hoc element to our theory in order to explain this away (eyewitnesses killed, the media are part of the conspiracy, all other evidence planted or changed etc). Hence, the application of Occam’s Razor would lead us to reject the unnecessarily complex conspiracy theory in favour of the much simpler explanation that explains the same observations with far fewer unproven assumptions.
In conclusion, conspiracy theories generally contain important factual mistakes and commit a number of errors of reasoning. They tend to move from some agency having something to gain from a particular state of affairs to the unjustified conclusion that therefore said agency actually brought about that state of affairs. Furthermore, they are overly sceptical of any evidence that goes against their theory, and overly credulous of any that supports it. By adding ad-hoc elements to the theory to explain away apparently contradictory evidence, they actually render the theory effectively unfalsifiable. They also tend to assume practically unlimited power and knowledge on the part of the conspirators. Whilst they might in principle be true, possible doesn’t mean probable, and conspiracy theories are, in general, far less plausible and parsimonious than the ‘official’ explanation.
Although small-scale and mundane conspiracy theories do of course take place all the time - and are regularly exposed as such - there is little reason to suppose that the sort of large-scale and hugely elaborate conspiracy theories beloved by conspiracy theorists are actually happening around us. Certainly the burden of proof is on the conspiracy theorists to provide the extraordinary evidence for such extraordinary claims, as they are the ones challenging the accepted and (at least prima facie) evidentially supported view – but this is a burden they have singly failed to meet so far.