Next to the propagation of the big lie, one of the most elementary and common devices in manufacturing propaganda is the notion that the truth is something you are not being told.
From conspiracy theorists to those selling patent medicine on the Internet, everyone who whispers the words “secret” and “mystery” is using this device.
But what happens when you already know you’re not being told the truth? The psychological impact is that much greater. Your normal inclination to be taken in by conspiracy theorists is all the more heightened when you know you are not being told the truth.