The Warden’s Unmarked Morning

At noon on Sunday, a judge tells a prisoner: “On exactly one weekday next week, you will be taken to the courtyard and hanged. The date will not be announced beforehand, and when you wake that morning you will not be able to know with certainty that the hanging must occur that day.” The prisoner argues that Friday is impossible: if he survives through Thursday, Friday would be the only remaining day, so it would not be a surprise. With Friday removed, the same reasoning rules out Thursday. Repeating the argument eliminates Wednesday, Tuesday, and Monday. He concludes that no hanging can take place under the judge’s conditions. The judge says nothing more. Is there still a weekday on which the sentence could be carried out while genuinely surprising the prisoner?