Thought experiment. Imagine there's a fifth dimension in which senses can flow, but physical structures can't be built. That is, line-of-sight isn't impeded by walls, and doors don't work (for blocking sight/sound). How would society be different? Containers would be indicators only; a building would be a hint to other autonomous beings not to intrude (how would this change evolution? Would the moral structures to support this become hardwired at a low level, a tacit agreement to ignore the fifth dimension becoming encoded in the genes? Or would it become an arms race? Or maybe it'd be gamed?). Walls are invisible, like forcefields. Or maybe like a topology: traversing a landscape of buildings is like crossing chasms and scaling cliffs. You'd have to be aware what was on the other side of a wall, space would be leaky. Or rather, the environment would be more insistant. Privacy becomes a question of distance. (Two similar thoughts: If you could see Paris from here, how big would it be? And: If you were on Europa, Jupiter would hang in the sky about twenty times the width of the Moon, or four palm-widths held at arm's length.)