The Illusion of Truth
The illusion of truth is a mechanism by which one comes to believe something is true when it’s not. In fact, they don’t just believe it; they also defend it as true. Also, they close themselves off to the possibility that it might be false.
The illusion of truth, also called the illusory truth effect, occurs because there’s a flaw in the processing of reality. As humans, we have the tendency to say that familiar things are true.
Source: Exploring Your Mind