All over the world, people accept conspiracy theories. ("The truth is out there.") Many people believe that high-level officials in the United States government were responsible for the assassinations of John F. Kennedy and Martin Luther King. Many people believe that AIDS was deliberately engineered by doctors. Millions of people believe that the attacks of 9/11 were undertaken by the United States or by Israel. Millions of people in the developing world believe that the United States is now plotting to conduct some nefarious campaign against them.
Conspiracy theories create an array of puzzles. What, exactly, are they? What counts as a conspiracy theory? Why do people accept conspiracy theories? Should government do anything about them? Adrian Vermeule and I try to make progress on these questions in a paper that is available here. For the moment, let us notice that a distinctive feature of conspiracy theories is their self-sealing quality: Those who hold such a theory are likely to be both motivated and able to fold contrary evidence into the theory itself, and even to conclude that the contrary evidence is further proof of the conspiracy. Often conspiracy theorists spend much of their time in isolated networks of like-minded others, which makes it all the more difficult to undermine their beliefs.
Some conspiracy theories are innocuous, fun, and funny. (On the innocuous and fun side, consider the parental conspiracies that give rise to widespread beliefs in Santa Claus and the Easter Bunny.) But some such theories are extremely dangerous, because they produce intense feelings of hatred and humiliation, and a real potential for violence. A serious task is to decide when it is worthwhile for government to try to debunk a conspiracy theory -- and to try to find ways to overcome the self-sealing quality of the theory through some form of infiltration.