st not argue too strenuously against it.

"Ingenious," he said.

_Ridiculous_, he thought to himself. _This man dismisses astrology and
approves greater absurdities._

"I myself suspected that the sun might be stationary while the earth
moves long before I learned that Aristotle might also believe so." Fra
Tomasso waved a hand toward the window again. His cell was the top floor
of one of the towers fortifying the Dominican chapter house, an anthill
of constant, mysterious activity. D'Aquino's window overlooked the north
side of Orvieto's wall. There was no covering on the window, and the
shutters were open to let in the cool mountain air. Daoud gazed upon the
rolling hills, bright green in the sunlight, beyond Orvieto's
battlements. This was a lovely country, he thought. Back in Egypt the
hills would be brown this time of year.

"Look how much light and heat we get from the sun," Fra Tomasso went on.
"Yet, the sun appears small--I can hide it with my thumb."

_Your thumb could hide four or five suns._

"Perhaps it _is_ small," Daoud said.

"If it is as big as it must be to produce such light and heat, it must
be very far away--thousands of leagues--to appear so small. But if it is
that far away, it must be bigger still, for its heat and light to travel
such a distance. The bigger it is, the farther away it must be--the
farther away it is, the bigger it must be. Do you follow? There must be
a strict rule of proportion."

Daoud told himself to ignore this nonsense and concentrate on the
important thing--that Fra Tomasso badly wanted a book by this pagan
philosopher Aristotle. That book might be the means of winning Fra
Tomasso. Not that he could be crudely bribed, but certainly such a
present would favorably dispose him to what Daoud had to say.

And he saw another way to make the point he had come to make.

"It may be, Your Reverence, that the book you want has been lost
forever. When I spoke of the destruction of Baghdad the other day, I
should have mentioned that the Tartars burned there a library rivaled
only by the great library of Alexandria in its prime."

His flesh turned cold. That was a mistake. In his zeal he had
momentarily forgotten that it was Christians who had destroyed the
library of Alexandria. As the story was often told in Egypt, when the
Muslim warriors took Alexandria from the Christians, they found that
most of what had once been the world's greatest collection of books had
been used to