The Tetrabiblos
Four books on astrology by Claudius Ptolemy, written in Alexandria around the middle of the second century CE. The Greek title is Apotelesmatika, “on effects”; Tetrabiblos, “four books”, is a later descriptive label, and the medieval Latin tradition knows the work as the Quadripartitum.
It is the most influential astrological text ever written in any language, and it is a poor guide to what astrologers of its own period were doing. Both things are true at once.
This entry is about the book. Its author, and the gap between what he wrote and what his name is attached to, are at Claudius Ptolemy.
What the work does
Book I sets out the physical apparatus: the qualities of the planets, the divisions of the zodiac, the aspects, the dignities. Book II covers what later tradition calls mundane astrology, the astrology of countries, weather and populations. Books III and IV cover the nativity, from conception and birth through the parts of life 1 bks. I-IV.
Ptolemy’s project throughout is to give astrology a physical rationale consistent with Aristotelian natural philosophy: the celestial bodies act on the sublunary world through heat, cold, moisture and dryness, and the doctrine follows from the physics. That project is what distinguishes him from the practitioners, and it is also why he is selective. He is arguing that the field can be made respectable, and he leaves out what will not fit 2.
What is missing from it
Several techniques central to the working Hellenistic corpus are absent or marginal in Ptolemy: the lots beyond the Lot of Fortune, much of the time-lord apparatus, and the elaborate topical machinery that fills Valens and Dorotheus. He also treats sect more lightly than the practitioners do 3.
Correction
Commonly saidThe Tetrabiblos is the standard textbook of Hellenistic astrology, so what it contains is what Hellenistic astrologers did.
The Tetrabiblos is the most-copied and most-translated astrological text, and its influence on everything after it is hard to overstate. It is far from a representative sample of the practice.
Ptolemy is writing a defence and a systematisation of a field he is not primarily a practitioner of, and the surviving technical manuals by working astrologers, Dorotheus, Valens, Paulus and the rest, contain a great deal that is not in him and organise what they share differently 32.
The difference is legible. Reading Ptolemy alongside Valens is one of the few places in ancient intellectual history where the gap between a theorist’s account of a discipline and a practitioner’s daily working notes can be laid side by side, and the comparison is available in print in English.
Two things in it that this site relies on
The definition of the tropical signs is here. Ptolemy takes the equinoctial and solstitial points as the beginnings of the signs and grounds the choice in the fact that those points are naturally determined whereas the constellation figures have no definite boundaries 1 bk. I ch. 11. This is the decisive passage against the claim that astrologers never noticed precession, and it is set out in Three Reference Frames.
The bounds table is also here, along with Ptolemy’s own account of where he got it: a damaged and hard-to-read manuscript whose general purport he says he could barely make out 1 bk. I. The consequences of that admission run through the whole later transmission and are treated in Essential Dignity.
Transmission, and why the edition must be named
The text reached the modern period through Greek manuscripts, a Byzantine paraphrase, Arabic translations and commentaries, and twelfth-century Latin translations made from the Arabic, before returning to the Greek in the Renaissance 4. Each stage left traces, and several of the disputed readings in the dignity tables can be traced to one branch rather than another.
Two consequences for citation practice, both of which this site follows.
Chapter numbering differs between editions. The chapter cited here as I.11 on the tropical signs appears under a different number in some reprints and translations, so every locus on this site names the edition it belongs to. The site uses the numbering of the standard English translation 1 and cites the critical edition of the Greek where a variant reading is at issue 5.
And a translation is a source with a date. The English text quoted here was made in 1940 and the Greek edition behind the variants in 1998; both are as datable as the second-century original, and where a translation is disputed this site names the translators and shows both readings.
Gap in the evidence
How the Tetrabiblos was received in its own century is not well evidenced. It is not clear how quickly it circulated, whether practitioners read it as a manual or as an apologia, or how Ptolemy’s physical rationale was regarded by astrologers who were not trying to make the field respectable to philosophers.
References
- Claudius Ptolemy, trans. F. E. Robbins. Tetrabiblos. Loeb Classical Library 435. Cambridge, MA: Harvard University Press, 1940 (composed c. 150 CE). bks. I-IV. find a copy (catalogue search) recordprimary source
The standard English reference and the chapter-numbering scheme this site adopts and names. Non-Robbins reprints number the chapters differently, so every locus here is given as Robbins numbering.
- Claudius Ptolemy, Wolfgang Hübner (ed.). Claudii Ptolemaei opera quae exstant omnia, vol. III.1: Apotelesmatika. Stuttgart and Leipzig: Teubner, 1998 (composed c. 150 CE). find a copy (catalogue search) recordscholarly
The critical edition of the Greek text, with the apparatus of variant readings.
- Tamsyn Barton. Ancient Astrology. London: Routledge, 1994. ISBN 0415110297 recordscholarly
- Roger Beck. A Brief History of Ancient Astrology. Oxford: Blackwell, 2007. find a copy (catalogue search) recordscholarly
The best short technical introduction to the Hellenistic system.
- Nicholas Campion. A History of Western Astrology, Volume II: The Medieval and Modern Worlds: Continuum, 2009. ISBN 9781441181299 recordscholarly
The companion volume, and the one that carries everything after the fifth century: its own description runs from the collapse of classical astrology to popular astrology in the twentieth century and its standing in the twenty-first. Volume I stops in the ancient and classical world, so a claim about the Renaissance, the Victorian press, the newspaper column or twentieth-century psychological astrology belongs here and not there. Listed by Bloomsbury Academic since Bloomsbury acquired Continuum in 2011; the 2009 printing is Continuum, and the ISBN is unchanged.