I feel like the prisoner's explanation is circular logic—akin to reducing something down to 0 = 0:<p>1. He claims he can't be executed on Friday, because it wouldn't be a surprise.<p>2. He then argues similarly that he can't be executed any other day.<p>3. He concludes therefore that he can't be executed.<p>But if "I won't be executed at all" was a possibility, then he could never even rule out Friday: on Friday, he'll either get executed, or not at all. Both are possible, so he can't claim an execution on Friday would be predictable beforehand.
Is the last part actually part of the paradox, or just a funny quip at the end. I found that bit quite hilarious, I could imagine that fitting into a Monty Python sketch or something quite well.<p>>The next week, the executioner knocks on the prisoner's door at noon on Wednesday — which, despite all the above, was an utter surprise to him. Everything the judge said came true.
What's interesting to me about this paradox is that it's (IMO) a clever repackaging of self-referential paradoxes: this statement is false, this statement can't be proven, etc.<p>In this case, it's "You will die on a day not deducible from this statement", but the self-reference is concealed by asserting it will be a "surprise".