"Earthman, the planet you lived on was commissioned, paid for, and run by mice. It was destroyed five minutes before the completion of the purpose for which it was built, and we've got to build another one." Only one word registered with Arthur.

"Mice?" he said.

"Indeed Earthman."

"Look, sorry - are we talking about the little white furry things with the cheese fixation and women standing on tables screaming in early sixties sit coms?"

Slartibartfast coughed politely.

"Earthman," he said, "it is sometimes hard to follow your mode of speech. Remember I have been asleep inside this planet of Magrathea for five million years and know little of these early sixties sit coms of which you speak. These creatures you call mice, you see, they are not quite as they appear. They are merely the protrusion into our dimension of vast hyperintelligent pan- dimensional beings. The whole business with the cheese and the squeaking is just a front."

The old man paused, and with a sympathetic frown continued.

"They've been experimenting on you I'm afraid."

Arthur thought about this for a second, and then his face cleared.

"Ah no," he said, "I see the source of the misunderstanding now. No, look you see, what happened was that we used to do experiments on them. They were often used in behavioural research, Pavlov and all that sort of stuff. So what happened was hat the mice would be set all sorts of tests, learning to ring bells, run around mazes and things so that the whole nature of the learning process could be examined. From our observations of their behaviour we were able to learn all sorts of things about our own ..."

Arthur's voice tailed off.

"Such subtlety ..." said Slartibartfast, "one has to admire it."

"What?" said Arthur.

"How better to disguise their real natures, and how better to guide your thinking. Suddenly running down a maze the wrong way, eating the wrong bit of cheese, unexpectedly dropping dead of myxomatosis, - if it's finely calculated the cumulative effect is enormous."