upon Friday-eve at the Takin gate of Nisapur. Now——" Tutush rose with a sigh and a smile, "—I who gather knowledge must go from thy house where knowledge is. Alas, I have caused thee much trouble."
When his guest had departed, Master Ali spent some time in cogitation. It seemed strange that he had been asked to observe Omar, whom he had suspected of observing him. And stranger still that he should be asked to write down the result. He wondered if the two had not exchanged some hidden message under his very nose, and he wondered why Omar should have been summoned to Nisapur. Master Ali saw everything with the eyes of suspicion.
Yet at the end of the month Master Ali had not succeeded in ferreting out Omar's secret. He could not understand why his pupil was indifferent to routine algebra and still eager to solve new problems. Certainly he seemed to depend upon no occult aid. Omar worked things out by mathematical formulas of his own. That was all—but not enough to satisfy the master's jealous curiosity.
In the last evening he tried to surprise Omar into confession, as he had tried before in the matter of the cubes.
"When wilt thou return to the Arranger of the World?" he asked casually.
Nizam al Mulk, the Arranger of the World, was the great Minister of the Sultan Alp Arslan, a power in the land, and the patron of Master Ali as well as Tutush.
"Return? I have never seen him."
'Then in the name of Allah, why art thou here?"
Omar explained that he had come to study. After the death of his father, Omar had made his home at the house of his milk-brother Rahim. But when he had returned from the war, Rahim's family had treated the foster son as a person of ill-omen—as if by Rahim's death Omar had forfeited his right to be in their house. They had taken Zoë from him to sell as a slave in the bazaar.
After that it had been unbearable to wander in the streets of Nisapur where he had made merry with Rahim, so he had sought the house of the distinguished teacher, hoping to bury himself in fresh work.
"And what is that work to be?" Master Ali pursued. "By what gate wilt thou leave the academy to enter the work of the world?
"But first," he suggested, "consider how wisdom hath been brought into this small world. The great wisdom hath been revealed by Prophets, who were never taught, but who had natural insight into that other world, the Invisible.
"The Prophets are the first among bearers of wisdom. The second are the Philosophers, who from study of the revelations of the Prophets and from acquired mastery of the sciences may explain to common men what would be otherwise hidden from them.
"First in order of time among the supreme Prophets was Moses, second was Jesus the Nazarene, and third was our lord Muhammad. That is sure. As to the Philosophers, different opinions are held. Alas for my ignorance I can only say that Plato and Aristotle and then our master Avicenna have woven the thread of wisdom into the warp of our poor minds.
"After the Philosophers come the Poets. Now the skill of a Poet is a dangerous skill, because his task is to excite the imagination, thereby making a great thing appear small, or a small thing great. By arousing anger or love, exultation or disgust, he causes the accomplishment of great things and petty things in this world.
"Since he stirs the imagination and cannot clarify the understanding, the art of a Poet is baser than the ability of a Philosopher. What poet's scribbling hath outlived the life of the singer?
"Whereas," Master Ali concluded, "the fruit of the labor of the mathematician never dies. He alone attains demonstrable truth, and he builds the solitary bridge from the unknown to the known. As algebra is the noblest branch of mathematics, I hope thou wilt devote thy skill to commenting upon the algebraic equations of the third degree."
Omar was stirred by the interest of the aged master. "I meant——" he searched for words to make clear his thoughts—"there are other