These tests can be applied to any conspiracy theory, be it the Apollo Moon Hoax, the Kennedy Assassination, or the various September 11 conspiracy theories.
It's remarkable how many conspiracy theories are based on arguments which are simply factually incorrect. If you're presented with a conspiracy theory argument, the first thing to do is to check the surrounding facts. Many incorrect arguments are repeated in ignorance. But it's also been my unhappy experience that there are some purveyors of conspiracy theories who knowingly repeat arguments they know are incorrect.
A second common problem with conspiracy theories is that they cloud the issue by attaching true, but irrelevant, arguments. Just because an argument is true doesn't mean it's relevant to the theory you're testing. This is a form of guilt by association, and gives the impression that the theory is being padded.
An argument on its own may appear to be plausible. But if we apply the argument to related fields or subjects, does it continue to make sense? Or would it require the world to be very different from how we see it?
There's a temptation to judge a theory simply by the number of supporting arguments, regardless of how they interact with each other. But amongst all these arguments, there's the danger that two or more of them contradict each other. This immediately means that at least one of the arguments is wrong, but in the context of conspiracy theories, it's perhaps worthwhile doubting both.
Conspiracy theorists often tout their apparent expertise with a body of knowledge in order to bolster their arguments. But, perversely, they also often decry other experts in the field. This is often because the expert consensus in that field is contrary to the argument presented. Similarly, they often quote experts speaking inaccurately outside their field of expertise.
An argument which merely expresses an opinion, but which doesn't have any supporting evidence, adds nothing to the theory, and should be ignored.
Some arguments are presented with weasel words such as "could have" or "maybe". Without any supporting evidence, these aren't arguments - they're just speculation. They too should be ignored.
There are cases when an argument presents two alternative explanations for an event. One is the conspiracy explanation, while the other is said to be the official explanation. When the official explanation is debunked, the conspiracy explanation appears to be correct by default. Problems arise, though, when the apparently official explanation turns out to be a straw-man misrepresentation of the official explanation.
Theories aren't built out of opposition to other theories. Instead, they're created to better explain the evidence than previous theories. Therefore, any conspiracy theory has to address evidence which contradicts it. Ignoring the evidence isn't acceptable, and should be treated as a major weakness of the theory.
Some conspiracy arguments rely on you accepting them without question, perhaps by an appeal to common sense. Sadly, common sense can lead us astray. This is where simple experiments, or even just careful observation of the world around us, can provide useful insights into the accuracy of an argument.
A problem with many conspiracy theories is that they exist only as a challenge to the official version of events. Yet if the conspiracy theory is true, a series of events must have occurred to bring the conspiracy to fruition. However, many conspiracy theorists aren't willing to spell out exactly how they think the conspiracy was achieved. This appears to be a tacit acceptance that their arguments don't add up to a coherent theory. What they often have, instead, is an ad hoc collection of arguments which, if put together, create an implausible, self-contradictory, and ad hoc narrative.
We thank Peter Barrett for providing these notes for publication.