A scholar and his city

Plan a short talk: decide what you say about his city, his patron, his books and how his work travelled. Mark which points the museum's record gives and which need another source.

Ibn al-Nadim, as the Cairo editors quote him, lists among al-Khwarizmi's books the Book of the Zij in its two versions known as the Sindhind, a book on the sundial, two books on using and making the astrolabe, and a book of history ². The editors list four surviving books that Ibn al-Nadim does not mention: the Book of Arithmetic, the Algebra, a book on the coordinates of countries explaining Ptolemy's views, and a fourth combining arithmetic, geometry, music and astronomy ³. The Encyclopaedia of Islam says his geography consists of lists of coordinates of the main towns and geographical features, in harmony with Ptolemy's, and corrects some of Ptolemy's errors, such as the excessive length of the Mediterranean ⁴. Its source of inspiration might have been the world map made for al-Ma'mun by a team of geographers that may have included al-Khwarizmi himself ⁴.

In his preface, the record on the algebra says, the author states that he wrote it with the encouragement of the caliph al-Ma'mun ⁵. For his other works the sources read for this lesson give no purpose in his own words. What they show is where he worked and under whom: the Encyclopaedia of Islam says that in his youth, under al-Ma'mun, he worked in the House of Wisdom of Baghdad ⁶, and that, if C. J. Toomer's datings are correct, almost all his main works were composed during al-Ma'mun's reign ⁶.

The sources differ on when he lived. The museum's data give his birth as about 164 AH and his death as about 235 AH, as reported, on one source, the Encyclopaedia of Notable Scholars and Men of Letters, and say they need an additional source ⁷. The Encyclopaedia of Islam places his life from about 184 to about 232 AH, that is about 800 to 847 CE ⁶. The Cairo editors hold that the dates of his birth and death are not known with certainty, and that he was a contemporary of al-Ma'mun, who ruled from 813 to 833 CE ^2 3. The museum does not choose between these dates ⁶.

The Cairo editors report that Suter believed al-Khwarizmi was one of those whom al-Ma'mun charged with measuring a degree of the earth's circumference; they add that some Arab historians say the Banu Musa took part in that task, and suggest that Muhammad, the eldest of the Banu Musa, was al-Khwarizmi himself, an inference of theirs rather than a report they quote ^3 8. The Encyclopaedia of Islam warns against confusing him with two other important men who bear the same nisba ⁶.

Suter believed al-Khwarizmi was among those charged with measuring a degree, and the Cairo editors suggest, as their own inference, that the eldest of the Banu Musa was al-Khwarizmi himself ^3 8. Defend your answer against the opposing case: would you put this in a short talk about him, and what would you say about how sure it is?

• Al-Khwarizmi: what Ibn al-Nadim, the Encyclopaedia of Islam and the Cairo editors say of his life and books.
• Baghdad: his city as the Encyclopaedia of Islam describes it.
• The Book of the Image of the Earth: one of four surviving books the Cairo editors say Ibn al-Nadim did not mention.
• The Banu Musa: Muhammad, Ahmad and al-Hasan, the sons of Musa ibn Shakir, as Ibn al-Nadim describes them.
• The Zij al-Sindhind: the astronomical tables Ibn al-Nadim mentions.