In this paper, I introduce a new paradox, the paradox of infallibility. Intuitively, this puzzle can be formulated in the following way. Assume that someone is infallible if and only if (iff) everything she believes is true and that there is an individual who believes exactly one proposition, namely the proposition that she is not infallible. Suppose that this individual is infallible. Then everything she believes is true. Hence, she is not infallible, since she believes that she is not infallible. So, if she is infallible, she is not infallible. Suppose that she is not infallible. Then everything she believes is true, since the only proposition she believes is the proposition that she is not infallible. Accordingly, she is infallible. Consequently, if she is not infallible, she is infallible. It follows that she is infallible iff she is not infallible. But this is clearly a contradiction. Hence, it cannot be the case that someone is infallible iff everything she believes is true and that it is possible that there is an individual who believes exactly one proposition, namely…

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