172 r Michael Katz
Number). The influence of the great ninth-century scholar Muhammad
al-Khwarizmi is manifest in these books. Al-Khwarizmi’s impact is also
noticeable in at least two other arithmetical manuscripts (in Hebrew and
Latin) that have recently been attributed (not unreservedly) to Ibn-Ezra.^1
Arguably, Ibn-Ezra was one of the first to convey to Europe the ideas of al-
Khwarizmi and with them certain fundamental doctrines of arithmetic.^2
Muhammad ibn-Musa al-Khwarizmi was a scholar in Caliph al-
Mamun’s celebrated “House of Wisdom” in ninth-century Baghdad. He
wrote extensively on mathematics and astronomy, and some of his writ-
ings were translated from Arabic into Latin, to be used as textbooks in
schools throughout Europe from the twelfth century if not before. His
best-known book is Kitab al-Hisab al-Jabr w’al-Muqabala (Book of Calcu-
lus of Completion and Balancing). The term algebra was coined from al-
Jabr and the term algorithm from al-Khwarizmi. Some scholars^3 maintain
that in writing this book al-Khwarizmi was influenced by (a translation
of) a Hebrew manuscript entitled Mishnat ha-Midot (Study of Measures,
by a mysterious Rabbi N). Other scholars^4 disagree, and they are probably
right. But that discussion is beyond the scope of the present essay.
Another well-known book of al-Khwarizmi is Kitab al-Hisab al-Hindi
(Book of Hindu Calculus), bringing to the Arab world, and later to Eu-
rope, some basic ideas of Hindu mathematicians. Also worth noting here
is al-Khwarizmi’s Istiqraj Tariq al-Yahud (Treatise on the Jewish Calen-
dar), where he discusses the nineteen-year cycle of the Hebrew calendar
as well as the specific dates of Rosh ha-Shana (Jewish New Year) and sev-
eral other Jewish festivals.
What we want to show in this essay is that al-Khwarizmi’s fundamental
principles were utilized by Ibn-Ezra not only in his mathematical writings
but also, in a subtle yet substantial manner, in his biblical commentary.
This is most clearly revealed in his extensive discussion of the Holy Name
in chapter 3 of the book of Exodus. And this will be the focus of our at-
tention in the present essay.
The Holy Name
The story of the first encounter between Moses and God is often devoutly
rehearsed and seldom fully understood. Perhaps hardest to understand
are the verses dealing with God’s name. We hear God speaking to Moses