“More than three centuries ago, Baruch Spinoza pointed out that the human mind cannot suspend disbelief in the truth or falsity of a statement and leave it hanging in logical limbo awaiting a “true” or “false” tag to be hung on it. To hear or read a statement is to believe it, at least for a moment. For us to conclude that something is not the case, we must take the extra cognitive step of pinning the mental tag “false” on a proposition. Any statement that is untagged is treated as if it is true. As a result, when we have a lot on our minds, we can get confused about where the “false” tag belongs, or can forget it entirely. In that case what is merely mentioned can become true. Richard Nixon did not allay suspicions about his character when he declared, “I am not a crook,” nor did Bill Clinton put rumors to rest when he said, “I did not have sexual relations with that woman.” Experiments have shown that when jurors are told to disregard the witness’s remarks, they never do, any more than you can follow the instruction “For the next minute, try not to think about a white bear.””
Pinker, Steven. The Sense of Style: The Thinking Person’s Guide to Writing in the 21st Century