"It's this," said the Time Traveler. "You must follow me carefully. I shall have to controvert one or two ideas that are almost universally accepted. The geometry, for instance, they taught you at school is founded on a misconception."
"Is not that rather a large thing to expect us to begin upon?" said Filby.
"I do not mean to ask you to accept anything without reasonable ground for it. You will soon admit as much as I want from you. You know, of course, that a mathematical line, a line of thickness nil, has no real existence. They taught you that? Neither has a mathematical plane. These things are mere abstractions."
"That is all right," said the Psychologist.
"Nor, having only length, breadth, and thickness; can a cube have a real existence."
"There I object," said Filby.