The castle of Reynard the Fox is the archetype of the foolproof refuge. Enemies may enter but may never lay their hands on slippery Reynard. False doors, secret chambers, hidden passageways, and multiple exits let Reynard either hide or escape. He may be watching his pursuers or he may be miles away, it’s impossible to say. In practice, however, a finite Maleperduis could always be surrounded, and a material Maleperduis could always be tumbled, so that an actual Maleperduis would need be infinite and insubstantial like, they say, heaven.