&gt; maybe the category &quot;conspiracy theory&quot; isn&#x27;t so useful?<p>Maybe not. The defining aspect of silly theories isn&#x27;t just that they involve conspiracies.<p>However many silly theories do wind up involving conspiracies, because assuming the existence of a conspiracy is the easiest way to explain away any differences between your theory and observable reality.<p>Think that President Obama comes from Mars? Well why is there a birth certificate that says he was born in Hawaii? Easy: someone faked it. Why didn&#x27;t the records office notice it was faked? They were in on it. Why hasn&#x27;t one of the President&#x27;s medical examinations shown up his Martian physiology? The doctor is also in on the conspiracy. Why didn&#x27;t anyone notice his spaceship landing? They did, the government covered it up. And so forth. There&#x27;s practically <i>no</i> fact you can&#x27;t explain away by asserting a giant conspiracy between all the people who tell us this fact.<p>Ridiculous conspiracy theories can usually be distinguished from vaguely sensible ones by looking at whether the asserted conspiracy would actually be a sensible way for the purported actors to achieve their goals. Ridiculous people claim that George W Bush plotted 9&#x2F;11 as a way to achieve... something, but always some goal that could have been achieved in a much easier and less risky way.<p>On the other hand, the idea that the CIA would build a giant ship to raise a Russian submarine while pretending it&#x27;s for some other purpose? That&#x27;s actually a sensible way for them to achieve an actual goal.