not at odds with Ptolemy’s (in fact, he cites the Almagest), and has the advantage of
being somewhat more rational than the available English versions of Tetrabiblos.
In the Tafhim,Al-Biruni begins his discussion of the oriental/occidental ques-
tion with the position of the planets relative to the Sun. He then shows that the supe-
rior planets become occidental when 90° from the Sun (the Sun having passed them).
They then go retrograde and later direct. Then comes the opposition. This divides the
circle into two parts; in one, the planet is oriental, and, in the other, occidental. Al-
Biruni does not say so, but he implies that the other half of the zodiac is handled in
the same way. With the inferior planets a different situation holds. Neither Venus nor
Mercury is ever 90° from the Sun, but both can be on either side of the Sun at an east-
ern or western elongation. The western elongation is oriental; presumably the eastern
is occidental. Al-Biruni asserts that planets in cazimi (within 16° of the center of the
Sun) are strongest. They are weakest when combust (the acceptable distance for this
varies from planet to planet) and are more powerful when oriental than when occi-
dental. There are various degrees of debility when occidental. They also change their
qualities of hot, cold, wet, or dry, depending on their relation to the Sun. Al-Biruni
asserts that the planets change their gender depending on their relation to the hori-
zon, though his discussion of this dimension of the problem of orientality and occi-
dentality is less clear than Ptolemy’s in Tetrabiblos(in Book III, chapter 3 of Robbins’s
translation, and Book III, chapter 4 of the Ashmand translation).
The last section of the Tafhimdeals with judicial astrology. It is here that the
author’s lack of examples is most disheartening. Case studies would have been helpful.
He divides the subject of astrology into five categories: (1) meteorology, (2) mundane
astrology relating to famine, plague, epidemics, etc., (3) environmental effects on the
individual, (4) human activities and occupations, and (5) a division including horary
and electional astrology. Al-Biruni says the foundations of this latter division are
unknown: “Here astrology reaches a point which threatens to transgress its proper lim-
its, where problems are submitted which it is impossible to solve for the most part, and
where the matter leaves the solid basis of universals for particulars. Where this bound-
ary is passed, where the astrologer is on one side and the sorcerer on the other, you
enter a field of omens and divinations which has nothing to do with astrology,
although the stars may be referred to in connection with them.”
What today is called natal astrology is subsumed under categories 3 and 4
(environmental effects and human activities and occupations). Al-Biruni considers
two initial points for natal astrology: the conception and the birth. He discusses find-
ing the hyleg and alcocoden for longevity. He finds the length of life through the
alcocoden (which he calls by its Persian name, kadkhuda). He defines the alcocoden as
the planet with the most dignity in the place of the hyleg. The number of years attrib-
uted to the native’s life is determined by whether the alcocoden is angular, succedent,
or cadent. Al-Biruni is less than complete and clear here. He says “a large number” is
given when the alcocoden is angular, “a mean number” when succedent, and “a small
number” when cadent. The tradition is more fully expounded in other medieval
works, such as Bonatti’s Liber Astronomiaeand Abu ̄ ‘Ali Al-Khayyat’s The Judgements
of Nativities.From the latter two books we learn that the numbers referred to come
from the Years of the Planets table. The rule varies from author to author, but is gener-Al-Biruni
[18] THEASTROLOGYBOOK