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When you do not know a fact you are ignorant. My question is what would you call the state of believing you know something that is false.

For instance suppose I see a black box and having opened it earlier, I know there is a rabbit in it. Some time later unbeknownst to me someone removes the rabbit. I still 'know' there is a rabbit in the box.

What do you call this state?

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There's always the Dunning-Kruger effect. –  Hot Licks Aug 15 at 15:50

6 Answers 6

up vote 5 down vote accepted

One word is mistaken.

  wrong in one’s opinion or judgement:
    she wondered whether she’d been mistaken about his intentions
      based on or resulting from a misunderstanding or faulty judgement:
        don’t buy a hard bed in the mistaken belief that it is good for you
        an unfortunate case of mistaken identity


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And, pace @Fortiter, a mistaken belief is easily proved to be wrong. –  St John of the Cross Mar 27 '13 at 8:04

Such a belief could be described as erroneous. Merriam-Webster defines erroneous as "containing or characterized by error: mistaken."

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I think that this example is merely a matter of ignorance: the person who believes that there is a rabbit in the box is ignorant of the fact that the rabbit was removed and, therefore, continues to believe something that once was true but has since changed and become false.

A better word than ignorant and mistaken, I think, is one of these:

tricked, bamboozled, conned, deceived, duped, misled

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All those words require deliberate action on the part of a third party, and while the OP's example does include that, it's not necessarily a required feature of the requested term. –  user867 Jun 5 '13 at 4:18

You believe that the rabbit is in the black box.

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Perhaps cognitive dissonance if you are aware of the contradiction or doublethink if you are unaware of any problem.

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I consider this "the state of false perception"

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Hello, Sam, and welcome to English Language & Usage. Your view appears to be in line with Plato's—or rather, with the character Socrates'—in his dialogue Meno, which attempts to distinguish 'truth' from 'true opinion' and 'false opinion.' I will gladly upvote your answer if you link it to some plausible discussion or argument in an authoritative source, but at the moment it reads simply as a personal opinion. –  Sven Yargs May 12 at 18:52
Ditto this comment to Mark? –  ab2 Aug 15 at 21:46

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