"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 fuel the fires that warmed the public baths. But, to Daoud's relief, Fra Tomasso only shut his eyes and shook his head, his cheeks quivering gently like a bowl of frumenty. "God forgive the Tartars." "God will certainly not forgive _us_, Fra Tomasso, if we help the Tartars to destroy Damascus and Cairo. Or Trebizond and Constantinople." The Dominican opened his eyes wide. "Constantinople?" "In the Far East they have taken greater cities and conquered much larger empires." Fra Tomasso crossed himself. "But it is God's will, even as Augustine tells us, that cities be destroyed and empires rise and fall. The Tartars may be the builders of a Christian empire that embraces the whole world." _God forbid it!_ Daoud was becoming exasperated with the fat Dominican's "perhapses" and "maybes." _Perhaps the earth moves and the sun stands still. Maybe the Tartars are God's means of making the whole world Christian._ He warned himself not to let his anger show. This might seem to be a pleasant conversation, but actually he was tiptoeing around the edge of a pit of quicksand. Still, if this clever, restless mind could be recruited to work against the alliance, how persuasive it would be. Daoud had already noticed that most of the leaders of Christendom listened when d'Aquino spoke. But Daoud dared not argue against the belief that God decided the fate of nations. He recalled a teaching of his Sufi master, Sheikh Saadi. He framed it in his mind to offer to d'Aquino.