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(religion, spiritualism, and occult)

Al-Biruni, whose full name is Abū’l-Rayhan Muhammad ibn Ahmad Al-Biruni, was born in 973 C.E. in what is now Khiva, Uzbekistan (formerly part of the Soviet Union). At the time of Al-Biruni’s birth, the area was a suburb of Kath, the capital of Khwarizm (north and northeast of ancient Parthia on the lower Oxus River in the region south of the Aral Sea). Known to the classical Greeks and Romans as Chorasmia, Khiva was the homeland of a people related to the Sogdian Magi who lived to the south and southeast of Khwarizm on the Oxus in the eastern reaches of what had once been the Persian Empire. The proximity of Al-Biruni’s general region, which was bordered on the east by the Hindu Kush, meant that Indian cultural and scientific traditions had certainly pervaded the region for centuries. Not far away, on the western shore of the Caspian Sea, lay the remnants of the Jewish empire of the Khazars, which had fallen to the duke of Kiev four years prior to Al-Biruni’s birth.

Only 23 years after Al-Biruni’s birth, the last of the Khwarizmshahs, Abū Abdallah Muhammad, a direct descendant of the Khusraws (the last dynasty of Persian kings before Islam), was overthrown by the Muslim emir Ma’mun ibn Muhammad. Thus, Persian-Magian traditions lingered in and around Al-Biruni’s birthplace. Indeed, despite the conversion to Islam, the whole region was steeped not only in Zoroastrianism but also in Manicheanism and astrological doctrines, as is apparent from Al-Biruni’s Chronologies of Ancient Nations, India and The Book of Instruction in the Elements of the Art of Astrology. The latter work, which was translated into English by R. Ramsay Wright in 1934, will hereafter be referred to by its Arabic short title, the Tafhim.

Thus, Al-Biruni came from a highly cultured society known for its mathematical, scientific, astronomical, and astrological lore. In his various works, Al-Biruni shows interest in, and familiarity with, the cultures and sciences of the peoples who surrounded him. He shows profound and advanced knowledge of scientific subjects. His mind was precise and he was a close observer of nature. He studied the Hindu numeral system and showed how to determine latitude and longitude accurately. When he visited India and viewed the Indus Valley, Al-Biruni concluded that it was an ancient sea basin filled with alluvium. In many ways, he was ahead of his time.

Al-Biruni traveled widely, leaving his birthplace for the Samanid court of Nuh ibn Mansur at Ghaznah in eastern Afghanistan, the Samanid capital, sometime after 990 C.E. In 998, he went to Gurgan with Qabus ibn Washmgir Shams al-Ma’ali. While there, Al-Biruni began his Chronology of Ancient Nations, which is dedicated to Qabus. In this work, completed in the year 1000, he shows advanced understanding of the comparative chronologies of the surrounding peoples. He seems to have returned to Khwarizm around age 37 and to have remained there until age 46, when his patron, Abū’l-’Abbas Ma’mun ibn Ma’mun, was murdered by rebellious subjects. As a result of the murder, Mahmud of Ghaznah invaded Khwarizm and subjugated the country, exiling its ruling class (and Al-Biruni with them) to Ghaznah in the following year. Al-Biruni served Mahmud as court astrologer, but somehow found time between 1016 and 1029 to travel to India and write his classic India, detailing the social, religious, and scientific characteristics of the Indians. During this period he also produced the Tafhim, his textbook on astrology and related subjects.

The Tafhim is a truly remarkable book in several respects. First, it is a medieval Oriental book dedicated to a woman. This by itself is remarkable. The woman, Rayhana bint al-Hasan, was a Persian noblewoman who was apparently a student of Al-Biruni’s while both were semicaptive at Mahmud’s court at Ghaznah. Virtually every paragraph of the Tafhim is interesting. Al-Biruni seems to have written both an Arabic and a Persian version. It contains 550 paragraphs plus a colophon that Al-Biruni tells us was intended as an aide-mémoire for Rayhana in the form of questions and answers. The 1934 Wright translation deletes this feature and presents a text arranged in paragraphs with headings. Though Wright’s translation shows signs of incompletion—it is typewritten, not typeset, with unpolished notes and comments, and clearly paraphrased in places—the overall composition and handling of the subject shows Al-Biruni to have possessed a mind of the highest quality and probity. As a teacher he must have been outstanding. He writes with clarity and conciseness uncharacteristic of medieval astrological writers. He tells us, at the very end of the book, that he has set forth what a beginner needs to know about astrology. He exceeds the modern standards in this regard and provides us with what amounts to an introduction to mathematics, geography, chronology, and astronomy before finally addressing judicial astrology.

As a textbook on astrology, the Tafhim is on a par with Ptolemy’s Tetrabiblos. Indeed, it is superior to it, in that it contains a good deal of material contained in Ptolemy’s Almagest as well. Much of the Tafhim is clearly an attempt to epitomize the Almagest. Its value is in the scope of its contents. In no other astrological work is there such a comprehensive survey of medieval astrological science and the subjects that supported it. The book reveals the many-faceted skills and duties of an eleventh-century Persian astrologer. Al-Biruni is also interested in the Hindu astrological traditions and how they differ or coincide with those with whom he is familiar. He also reports Magian astrological practices. The shortcoming of the book is that, written as an aide-mémoire, it lacks examples showing how to apply the methods, astrological or mathematical, so thoroughly set forth. However, the book does provide a uniquely clear window into the level of knowledge attained by a Persian astrologer in 1029. By comparison, his European counterparts were deprived.

Al-Biruni’s exposition of astrology places the subject squarely in the context of the mathematical disciplines. He begins by introducing the student to geometry and arithmetic to provide the would-be astrologer with the ability to calculate. The calculations are pre-logarithmic, and geometrical trigonometry is used. Curiously absent is any mention of the forty-seventh proposition of Euclid, also known as the Pythagorean theorem, which Ptolemy used to such good effect in the first book of the Almagest to find the lengths of chords subtending arcs of the circle.

Al-Biruni’s discussion of arithmetic is Pythagorean, based clearly on Nicomachus’s Introduction to Arithmetic. Initially, this seems strange and possibly even esoteric, until one realizes that ancient calculation in the Middle East, insofar as it was based on Greek mathematics, was based on theoretical arithmetic such as Nicomachus’s. As late as the thirteenth century, this was still true in Europe. For instance, Guido Bonatti, in Liber Astronomiae, asserts that the art of calculation has to do with the knowledge of numbers and tables, such as the multiplication tables and tables of roots and powers either found in Nicomachus’s work or suggested by him. In practice, such tables were used in conjunction with the abacus. Throughout the geometry and arithmetic sections, he emphasizes ratio and proportion. As in Ptolemy’s Almagest, the solution of triangles relies on the application of areas and the Pythagorean theorem.

For reasons he does not make clear, Al-Biruni discusses conic sections in the Tafhim, an example of the aide-mémoire character of this text. Clearly he must have explained the relevance of conic sections to astrology to Rayhana, but he does not make it clear to the reader. If it were not known that scientists in his day (and even in Ptolemy’s day) knew that light expanded in cone shapes, and that the theory was fairly widely held that astrological influence was transmitted from heaven to earth via the light of the stars, there would be no hint as to why he included this discussion at all.

Al-Biruni also includes a discussion of the five regular Platonic polyhedra, equating them, in good Neoplatonic fashion, with the five elements. Paragraph 107 treats the powers of numbers from the first power to the fourth. Paragraph 108 presents the eleventh-century Persian understanding of the decimal notation of the Hindus, including the use of the cipher as a placeholder. Al-Biruni’s handling of arithmetic includes an introduction to algebra, which, in his day, was truly “occult.” The laws regulating it were not yet known, and his very short exposition shows this fact by its incompleteness. Al-Biruni then introduces astronomy, beginning with the sphere. Step by step he explains basic geocentric astronomy, discussing the celestial circles, their subdivisions, the movements of the luminaries (the Sun and Moon) and the planets, the constellations, and the planetary theories of his day. He, like John Dee, brings his geocentric astronomy into his geocentric astrology (paragraph 387), interpreting the meaning of planets at perigee and apogee and on different places on their epicycles. He discusses and voices skepticism about the trepidation theory, which held that the precession of the equinoxes was not constant in a retrograde direction but oscillated back and forth—an incorrect idea first put forth by Thabit ben Qurrah in the tenth century. He discusses the World Days and Year according to the Persian astrologer Abū Ma’shar and the Hindu conceptions of yugas (the four ages of Hindu world cycle), kalpas, and manvantaras as found in the Siddhantas.

Al-Biruni next discusses the size and distance of the planets and elements, the distribution of the land and water masses, and terrestrial longitude and latitude. He discusses the gnomon (a kind of sundial) and its shadow (so basic for chronology) in between discussing details of the horizon system of celestial coordinates (azimuth and altitude).

Having prepared the student with the basics, Al-Biruni then discusses geography, including the seven climates, their extent, and their characteristics. His presentation of the various cities in the climates shows that, although he has a fairly accurate mathematical sense of the terrestrial globe, his knowledge of exact latitude and longitude on Earth is approximate. One of the surprises of this book is Al-Biruni’s mention in paragraph 239 of the mythological mountain Meru (the World Axis), under which angels dwell, and the island Lanka (modern Sri Lanka), where the demons dwell. This lore is Indian, not Persian, and definitely not Islamic. Could it be that the Persian Al-Biruni sought to keep ancient traditions common to both Iran and Aryan India alive? Likewise, paragraph 240 contains another surprise—red as well as white men lived in northwestern Europe. He clearly means red-skinned men, as in every one of the other cases in which he identifies the denizens of the various regions of the world by their skin color. Could it be that he was repeating reports of contact between the Viking Rus (who were in the Volga basin and Byzantium in his day) and the Amerindians?

In paragraph 242, Al-Biruni returns to astronomy to pin down with what degree a given star will culminate, rise, or set. In paragraphs 245–48 he addresses the houses of the horoscope, using equal houses from the ascendant. Next he discusses the astronomy of the anniversary on the macrocosmic level as a “Revolution of Years of the World” in medieval parlance (Aries ingress in modern) and on the microcosmic level as a solar return for an individual. Paragraph 250 deals with the Saturn-Jupiter conjunctions. Lunar motion follows, with a discussion of the phases of the Moon followed by a presentation on eclipses and the problem of parallax.

Next Al-Biruni switches to the problems of chronology, showing that the astrologer of his day was called upon to regulate the calendar and to understand how the calendar of his nation related to those of other nations who used different systems of chronology. He discusses leap years, solar and lunar years, intercalation, and the religious festivals of various peoples of the Middle and Far East, including the Indians and Sogdian Magi. There follows a description of the astrolabe and its use in astronomy, desert navigation, and trigonometrical measurements.

After the astrolabe, Al-Biruni returns to the subject of astrology, discussing the zodiacal signs and their correspondence to directions of the compass, professions, character, appearance, diseases, crops, and animals. Next he shows the relation of the signs to each other, the year, and the triplicities. He then expounds on the planets with their various correspondences. Some of his correspondences seem a bit beside the point or of little importance; for instance, he lists pimples as a Cancer “disease.” Paragraph 348 presents us with a surprise, stating that the planets have a tendency to take on the gender of the sign they are in. This seems to mean that even male planets become effeminate in female signs! He discusses the Years of the Planets table found so frequently in medieval texts and consisting of Least, Mean, Great, and Greatest Years (used in predicting longevity). He confesses that he doubts that people ever lived as long as the Greatest Years (e.g., the Sun’s Greatest Year is 1,461 years). He clearly does not know how to use the Greatest Years of the Planets. He then launches into the dignities and debilities of the planets, their friendships and enmities, and the halves of signs, decans, paranatellon, terms, ninths (nawamsas), and twelfths (dwadasamsas). He gives characteristics of individual degrees. Correspondences of the houses follow in natal and horary figures. The Arabic parts are discussed in paragraphs 475–80. The subject of application and separation is then addressed. He follows with more on dignities.

The vexed question of the oriental/occidental positions of the planets (i.e., whether they are in the left or right hemisphere of a horoscope) and the effect this has on their influences is the subject of paragraphs 481–86. The orientality or occidentality of the planets is found obscurely in Dorotheus’s Pentateuch (first century C.E.) and gets a fuller and thoroughly problematical treatment in Ptolemy’s Tetrabiblos (second century C.E.). Al-Biruni’s treatment is based on Al-Kindi’s. It is systematic, ultimately 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 question with the position of the planets relative to the Sun. He then shows that the superior 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 eastern 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 occidental. 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 horizon, though his discussion of this dimension of the problem of orientality and occidentality 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 Tafhim deals 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 limits, 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 boundary 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 finding 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 attributed 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 Astronomiae and Abū ‘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 generally that Great Years are given when the alcocoden is angular, the Mean Years when it is succedent, and the Least Years when it is cadent. Yet, in addition to this, Al-Biruni, following Ptolemy, still tries to predict the exact time of death by directing the hyleg to the place of the Apheta. His complete method, therefore, is twofold and seems to be a fusion of two techniques originally used independently of each other.

He employs solar returns and progressions as well as the divisor (Ruler of the Year by profection of the ascendant) for discovering the important events in the native’s life each year. He directs by profection (down to the week) and by term from year to year. He discusses rectification by the animodar of Ptolemy and the trutine of Hermes. Feeling assured that he has set forth the knowledge necessary to a beginner, he warns readers not to exceed the limits of the knowable and thereby bring scorn and derision upon themselves.

Such then is Al-Biruni’s Tafhim. It is certainly one of the classic works in astrology and should be closely studied by all interested in the history and practice of traditional astrology. It opens a window onto the astrological and mathematical expertise of one of the world’s finest astrological minds. Al-Biruni was highly regarded in his day, and his work was preserved and transmitted. As mentioned, it was a source for Guido Bonatti’s thirteenth-century Liber Astronomiae, which was itself highly influential. Except for its failure to provide practical examples, the Tafhim constitutes a veritable treasure trove of astrological lore.

—Robert Zoller


Albiruni’s India. Translated by Edward C. Sachau. Delhi: S. Chand & Co., 1964.
Al-Khayyat, Abū ‘Ali. The Judgements of Nativities. Translated by James H. Holden. Tempe, AZ: American Federation of Astrologers, 1988.
The Book of Instruction in the Elements of the Art of Astrology. Translated by R. Ramsay Wright. London: Luzac & Co., 1934.
Dorotheus. Pentateuch (published as Carmen Astrologicum, by Dorotheus Sidonius). Translated by Pingree. Leipzig, Germany: B. G. Teubner, 1976.
Hoyt, Edwin P. Arab Science. New York: Thomas Nelson, 1975.
Ptolemy, Claudius. Ptolemy, Tetrabiblos. Translated by F. E. Robbins. Cambridge, MA: Harvard University Press, 1964.
Ptolemy, Claudius. Ptolemy’s Tetrabiblos. Translated by J. M. Ashmand. London: Foulsham & Co., 1917.
Shumaker and Heilbron. John Dee on Astronomy: Propaedeumata Aphoristica 1558 & 1568. Berkeley: University of California Press, 1978.