The example below came to me about a year ago, and has had my thinking in circles ever since. I would call it circular reasoning, were it not that this example can be resolved logically in the end.

<<>>

We will pretend that a person named Ruth said, "I have such a good conscience that every time I tell a lie, I have to confess it the very next minute." Then she adds quickly, "Whoops, that was a lie!"
The question is, Did she just lie? And if so, which of her statements was the lie? You might easily say that it is the first one, for she admits that she lied by saying it. But then she has just confessed it in the next minute, therefore proving her first statement to be true. This would mean her second statement was a lie.
If her first statement was true, and her second one a lie, than she would confess the very next moment that saying, "whoops, that was a lie," was a lie. And since she does not confess it, than we must assume that the first statement is true.
By then, we are back to the beginning......

We could resolve it partly be saying that the first statement is a lie, in that, Ruth does not tell the truth the very next moment every time, and therefore her confession in her second statement is true.