The unexpected hanging paradox poses a famous problem that has yet to be resolved. Despite significant interest from several schools of thought, no final resolution has been established. The paradox goes like this: There is a prisoner waiting to be executed. The guards tell the prisoner he will be hanged at noon on a weekday, but they don't tell him exactly when, just that he'll be surprised on the morning of the execution. The prisoner rules out Friday as a potential day of his execution, because if he were alive at noon on Thursday, a Friday execution wouldn't come as a surprise. And since he can't be hanged on Friday, the prisoner rules out Thursday, because if he were alive at noon on Wednesday, a Thursday execution wouldn't be a surprise, either. By this same logic, the prisoner rules out all of the other days of the week. Yet, when the prisoner was executed on Wednesday, he was completely surprised. Where was the flaw in the prisoner's logic? This paradox has been called a significant problem for philosophy.