where water is scarce. To this day Spanish agriculture profits by Arab irrigation works.
The distinctive culture of the Muslim world, though it began in Syria, soon came to flourish most
in the Eastern and Western extremities, Persia and Spain. The Syrians, at the time of the conquest,
were admirers of Aristotle, whom Nestorians preferred to Plato, the philosopher favoured by
Catholics. The Arabs first acquired their knowledge of Greek philosophy from the Syrians, and
thus, from the beginning, they thought Aristotle more important than Plato. Nevertheless, their
Aristotle wore a Neoplatonic dress. Kindi (d. ca. 873), the first to write philosophy in Arabic, and
the only philosopher of note who was himself an Arab, translated parts of the Enneads of Plotinus,
and published his translation under the title The Theology of Aristotle. This introduced great
confusion into Arabic ideas of Aristotle, from which it took Arabic philosophy centuries to
recover.
Meanwhile, in Persia, Muslims came in contact with India. It was from Sanskrit writings that they
acquired, during the eighth century, their first knowledge of astronomy. About 830, Muhammad
ibn Musa al-Khwarazmi, a translator of mathematical and astronomical books from the Sanskrit,
published a book which was translated into Latin in the twelfth century, under the title Algoritmi
de numero Indorum. It was from this book that the West first learnt of what we call "Arabic"
numerals, which ought to be called "Indian." The same author wrote a book on algebra which was
used in the West as a text. book until the sixteenth century.
Persian civilization remained both intellectually and artistically admirable until the invasion of the
Mongols in the thirteenth century, from which it never recovered. Omar Khayyám, the only man
known to me who was both a poet and a mathematician, reformed the calendar in 1079. His best
friend, oddly enough, was the founder of the sect of the Assassins, the "Old Man of the Mountain"
of legendary fame. The Persians were great poets: Firdousi (ca. 941), author of the Shahnama, is
said by those who have read him to be the equal of Homer. They were also remarkable as mystics,
which other Mohammedans were not. The Sufi sect, which still exists, allowed itself great latitude
in the mystical and allegorical interpretation of orthodox dogma; it was more or less Neoplatonic.
The Nestorians, through whom, at first, Greek influences came