I suppose Wednesday was not required, but if you accept the story as it is told, then it is counterfactual to ask “what if the prisoner was still alive on Thursday evening”. But even if he were, since he deduced that he couldn’t be hanged, he would be surprised even then, after the hangman appeared on Friday. (Some interpretations may require the hanging to happen sooner than Friday to preserve paradoxness.)
This comment links to a good article by Chow, where he analyses the paradox in detail from different points of view, and shows that there is indeed a contradiction in one specific (reasonable) interpretation of the paradox, but it isn’t apparent because the interpretation relies on self-referential formulation of the problem. It is far less clear than “X says A, Y says not A, both are right”.
Sorry for misinterpretation, then.
I suppose Wednesday was not required, but if you accept the story as it is told, then it is counterfactual to ask “what if the prisoner was still alive on Thursday evening”. But even if he were, since he deduced that he couldn’t be hanged, he would be surprised even then, after the hangman appeared on Friday. (Some interpretations may require the hanging to happen sooner than Friday to preserve paradoxness.)
This comment links to a good article by Chow, where he analyses the paradox in detail from different points of view, and shows that there is indeed a contradiction in one specific (reasonable) interpretation of the paradox, but it isn’t apparent because the interpretation relies on self-referential formulation of the problem. It is far less clear than “X says A, Y says not A, both are right”.