Astrology

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Astrology is the practice of reading meaning in the heavens — the positions and movements of the sun, moon, planets, and stars taken as bearing on events on earth and on the course of an individual life. For most of recorded history it was not a fringe pursuit but a learned discipline, taught alongside astronomy and medicine, and the two studies of the sky were a single enterprise long before they were divided.

Its documented roots lie in Mesopotamia, where scribes kept records of celestial events and read them as omens for the king and the realm — a flooding, a war, the fate of a harvest. This was astrology of the state, not yet of the person. The decisive turn came in the Hellenistic world, where Babylonian observation met Greek geometry and Egyptian lore to produce the natal horoscope: a chart of the sky at the moment of a birth, divided into twelve signs and twelve houses, read for the character and destiny of one human being. That system — the zodiac, the planets bearing the names of gods, the aspects between them — is the ancestor of nearly all later Western astrology, and it was codified above all in the second-century handbook of Ptolemy, who gave the practice the prestige of a natural science.

Astrology travelled wherever the learning of late antiquity travelled. It was elaborated by astronomers of the medieval Islamic world, returned to Latin Europe through their texts, and stood near the centre of Renaissance intellectual life, where princes kept astrologers and physicians timed their treatments by the stars. It also developed independently and along different lines in India and in China, each with its own scheme of houses, signs, and significations; the resemblances among these systems are real and partly the trace of shared transmission, but they are not one tradition, and each must be read in its own terms.

The claim at the heart of the art is that the heavens and earthly life correspond — that the sky is legible. Practitioners have understood this in more than one way: some held the stars to be causes, their light and motion physically shaping events below; others took them as signs only, a clock or a mirror rather than a force, on the principle that the pattern above and the pattern below move together without one compelling the other. The difference mattered, because the stronger claim collided directly with human freedom, and theologians from Augustine onward attacked astrology precisely where it seemed to make fate mechanical. Philosophers raised the same problem from within: Plotinus, granting that the stars might signify, denied they could compel the soul.

The split between astrology and astronomy came late. Through the seventeenth century many of the figures who founded modern astronomy still cast horoscopes, and the separation hardened only as the new physics offered a heavens with no room for meaning in it. Astrology lost its standing as a science and persisted as something else — a symbolic language, a tradition of divination, a frame for reading a life. What it had always offered was a way of placing the individual inside a larger order, and of treating the moment of a birth as something the whole cosmos was party to.

→ In the library: Plotinus — The Enneads (MacKenna): Are the Stars Causes?

→ Related: Divination · Mesopotamia · Neoplatonism · Alchemy · Hermes Trismegistus