"Look at the roof and the floor here. The upper extreme is the roof, that's an 'abiding'. The lower extreme is the floor, and that's another 'abiding'. But in the empty space between the floor and the roof there's nowhere to stand. One could stand on the roof, or stand on the floor, but not on that empty space. Where there is no abiding, that's where there's emptiness, and Nibbana is this emptiness."