What Keeley is referring to here includes what’s come to be known as conspiracy theory’s “self-sealing” characteristic: if evidence against the conspiracy theory comes from a new source Y, the theory expands to include Y as part of the conspiracy. This self-sealing property is key to how global warming denialists have come to believe that vast majority of the world’s climate scientists are involved in perpetuating a “hoax,” as Donald Trump has called it. “As a result of this process,” Keeley writes, “an initial claim that a small group of people is conspiring gives way to claims of larger and larger conspiracies.”