Not so. If the wall works, then being a rationalist will allow you to correctly interpret the evidence of that fact, while irrationality might cause you to ignore the evidence and incorrectly conclude that the wall has no effect.
Something other than the wall could grant your wish to believe that the wall grants wishes, and then you would believe a falsehood. (Unless the wall grants wishes, too, but ignored yours in particular for some reason. But that’s a Gettier case.)
Not so. If the wall works, then being a rationalist will allow you to correctly interpret the evidence of that fact, while irrationality might cause you to ignore the evidence and incorrectly conclude that the wall has no effect.
A better wish might be “I wish to believe that this wall grants wishes.” If the wish is granted, then you will believe truth; and if it is not granted, then you will also believe truth.
Something other than the wall could grant your wish to believe that the wall grants wishes, and then you would believe a falsehood. (Unless the wall grants wishes, too, but ignored yours in particular for some reason. But that’s a Gettier case.)
p(wishgranted|~wallgrants) is negligible, I think. Still, I suppose you could just recite the entire Litany of Tarski.
What is p(wish is answered by Murphy the mad god of irony)?