The Doctor stops his half-distracted tinkering with this and that before looking up. This is going to be a bit complicated to explain, or so he expects.

"There's only one void-or at least I'm pretty sure." Which, coming from him means that he's probably right. He's been known to be wrong on occasion but not normally. "The Void is... er... Think of a wall in a house-the void is the space in between the walls-except the walls, in this case, are the different universes."