If the reason for keeping it private is that he plans to do the trick with more people (and it doesn’t work if you know the method in advance) than it makes sense. But otherwise, I don’t see much of a difference between somebody thinking “there is no argument that would convince me to let him out” and “argument X would not convince me to let him out”. In fact, the latter is more plausible anyway.
In any event, I am the type of guy who always tries to find out how a magic trick is done and then is always disappointed when he finds out. So I’m probably better off not knowing :)
If the reason for keeping it private is that he plans to do the trick with more people (and it doesn’t work if you know the method in advance) than it makes sense. But otherwise, I don’t see much of a difference between somebody thinking “there is no argument that would convince me to let him out” and “argument X would not convince me to let him out”. In fact, the latter is more plausible anyway.
In any event, I am the type of guy who always tries to find out how a magic trick is done and then is always disappointed when he finds out. So I’m probably better off not knowing :)