Recall that absolute geometry is the set of statements that can be deduced from Euclid's first four postulates. Then existence of parallel lines is certainly a theorem of absolute geometry, while the question being addressed by most of the mathematicians discussed in this section is whether uniqueness of parallels is also a theorem of absolute geometry.

‘He was still booking them in for their check-ups. All that cholesterol to be tested, all those urinalyses.’

The second adjustment [to a door that keeps swinging open] will require the screws to be loosened, and a shim or packing piece pushed behind the hinge to bring it into line.

Two years of his life were spent at this elevating game, during which time he had only eighty-two fights with fond mothers who felt that he had been either neglectful of their particular children or had ruthlessly given them the rinky-dink.