times forbidden as a private practice, astrologers continued to be consulted by the
court. As the empire became Christianized, the Christian church began to officially
oppose certain kinds of astrology in the fourth century C.E. (for example, in the writ-
ings of the Council of Laodicea).
During Hellenistic times, astrology began to bloom in Egypt through the
Alexandrian school, where Babylonian and Egyptian astrological lore mingled with
Greek philosophy. The earliest Greek Hermetic literature, in the second century
B.C.E., focused on astrology. Fragments of these texts, among which are the Salmes-
chiniaka and the textbook of Nechepso and Petosiris, have survived in the Catalogus
codicum astrologum Graecorum,as quotations in some Arabic works of the ninth cen-
tury, and in later Latin writings. Within the Hermetic tradition, iatromathematics, or
medical astrology (through which the various anatomical parts are associated with
planets, herbs, and minerals), also developed, deriving its name from the Greek iatro-
mathematikos.A poem on astrology, “Astronomica,” of which five books still exist, was
composed in the early first century C.E. by Manilius. He compiled contemporary
knowledge of this science, often in contradictory forms and under the influence of the
Stoicist vision of cosmic sympathy and correlation between macrocosm and micro-
cosm. In the second century C.E., Vettius Valens, an Antiochian intellectual operating
in Alexandria, Egypt, compiled the Anthology,a work on astrology that shows the new
concept of this field as a secret art learned through initiation.
Ptolemy, one of the most influential intellectuals in the history of Western
astrology, also lived in Alexandria in the second century. His main works were the
Almagest(Greek, meaning “greatest”) and the Tetrabiblos(Quadripartitumin Latin).
The Almagestwas an astronomy work that taught how to predict celestial phenomena,
mostly through the use of mathematics. The Tetrabiblosbecame a major text for
astrologers and occultists in the western world for several centuries. Ptolemy gathered
the knowledge of Egyptian and Chaldean astrology and interpreted it in the light of
Greek philosophy, Stoicism in particular. The Stoic idea that all matter is bound
together in a cosmic sympathy became a rational explanation for the relationship
between the changes in the universe (macrocosm) and in man (microcosm). Magic
and such traditions as number symbolism, chiromancy, and geomancy became
attached to astrological divination, although these did not change the basic principles
of astrology.
Ptolemy’s work was authoritative for centuries, particularly in Constantinople
(Byzantium), the capital of the eastern part of the empire, where Greek remained the
spoken language. In 500 C.E., Rhetorius introduced, among other new elements, the
division of the signs of the zodiac into triplicities, corresponding to the four classical
elements (still used in modern astrology). Although some theological schools in
Byzantium accepted astrology, several Christian emperors (such as Constantius, Teo-
dosius, and Valerianus) began to proscribe astrology and threatened astrologers with
exile. Earlier, in the fifth century, in the Platonic Academy of Athens, the last bul-
wark of the Greek pre-Christian culture, Proclo (410–485) had commented on the
Tetrabibloswith regard to the stars as a “secondary cause of earthly events.” But in 529,
the emperor Justinian (527–565) closed the academy, claiming it was a center of
pagan thinking, and many of the scholars from Athens fled to Persia and Syria.History of Western Astrology
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