A broader point is that conspiracy theories overestimate the competence and discretion of officials and bureaucracies, who are assumed to be able to make and carry out sophisticated secret plans, despite abundant evidence that in open societies government action does not usually remain secret for very long.20 Recall that a distinctive feature of conspiracy theories is that they attribute immense power to the agents of the conspiracy; the attribution is usually implausible but also makes the theories especially vulnerable to challenge. Consider all the work that must be done to hide and to cover up the government’s role in producing a terrorist attack on its own territory, or in arranging to kill political opponents. In a closed society, secrets are not difficult to keep, and distrust of official accounts makes a great deal of sense. In such societies, conspiracy theories are both more likely to be true and harder to show to be false in light of available information.21 But when the press is free, and when checks and balances are in force, government cannot easily keep its conspiracies hidden for long. These points do not mean that it is logically impossible, even in free societies, that conspiracy theories are true. But it does mean that institutional checks make it unlikely, in such societies, that powerful groups can keep dark secrets for extended periods, at least if those secrets involve important events with major social salience.
An especially useful account suggests that what makes (unjustified) conspiracy theories unjustified is that those who accept them must also accept a kind of spreading distrust of all knowledge-producing institutions, in a way that makes it difficult to believe anything at all.22 To think, for example, that U.S. government officials destroyed the World Trade Center and then covered their tracks requires an ever-widening conspiracy theory, in which the 9/11 Commission, congressional leaders, the FBI, and the media were either participants in or dupes of the conspiracy. But anyone who believed that would undercut the grounds for many of their other beliefs, which are warranted only by trust in the knowledge-producing institutions created by government and society. How many other things must not be believed, if we are not to believe something accepted by so many diverse actors? There may not be a logical contradiction here, but conspiracy theorists might well have to question a number of propositions that they seem willing to take for granted. As Robert Anton Wilson notes of the conspiracy theories advanced by Holocaust deniers, “a conspiracy that can deceive us about 6,000,000 deaths can deceive us about anything, and [then] it takes a great leap of faith for Holocaust Revisionists to believe World War II happened at all, or that Franklin Roosevelt did serve as President from 1933 to 1945, or that Marilyn Monroe was more ‘real’ than King Kong or Donald Duck.