A conspiracy is: a secret plan, by two or more people, to commit an immoral or subversive action, against another person or group, without their knowledge or consent.
The assassination of the Australian archduke Franz Ferdinand was a conspiracy; the assassination of John F. Kennedy was not.
How can we tell the difference between a conspiracy fact and conspiracy fantasy? Here are some of the characteristics of a conspiracy theory that indicate that it is likely untrue:
1. The more complex the conspiracy, and the more elements had to be in place for it to unfold successfully, the less likely it is to be true.
2. The more people involved in the conspiracy, the less likely they all will keep silent or be kept silent.
3. The grander the conspiracy – for example, world domination – the less likely it is to be true. How likely is it that a small group of evil spirited people actually control the whole world behind the curtains?
4. There is claimed to be a connection between events, but no evidence is offered. The chain of events can be equally or better explained by another theory.
5. The agents that are accused of conspiring are elevated to near superhuman power. How likely is it that even the most carefully planned conspiracy will run smoothly; that not one error is made?
6. The more the conspiracy theory assigns portentous and sinister meanings and interpretations to what are most likely innocuous or insignificant events, the less likely it is to be true. Is there really no moral capitalists, bankers or politicians? Are all government agencies or private organizations corrupt?
7. If the proponents of a theory defends it to the point of refusing to consider alternative explanations for the events, rejecting disconfirming evidence and seek only data that seem to support their views, then they are likely wrong and the conspiracy is probably a figment of their imagination.
Shermer, M. (2011). The Believing Brain. New York: Times Books.