hong ... actually, rereading the spell descriptions again, all this business about hitting the wall being "incontrovertible proof" or not is irrelevant! A major image _disappears_ if it's struck by an opponent. If you want the wall to hang around after being hit (albeit with the club passing through), you need illusory wall.
Grundle said:
OK. You good...
"The image disappears when struck by an opponent unless the character causes the illusion to react appropriately."
But what about the following scenario...
What about an illusion of a wraith or shadow or some other incorporeal being? would "striking" such an illusion constitute incontrovertible proof of an illusion?
Grundle said:The wraith or shadow would disappear when hit, unless the caster is around to make the illusion "react appropriately".
A "real" wraith would be unaffected by non-magical weapons. The weapon wouldn't connect with anything - just like our "illusory" wraith. Hard to tell the difference (right?)

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.