Claudius Ptolemy
Claudius Ptolemy worked at Alexandria in the second century CE and produced the technical astronomy, the geography and the astrology that the following fourteen centuries treated as authoritative 12. Thirty-seven entries on this site mention him, more than any other name.
This entry is about the man and about his name. The book is a separate entry. What the Tetrabiblos contains, how it is organised, and why its chapter numbers have to be cited are at The Tetrabiblos; the astronomical work is used at Precession of the Equinoxes. What is left, and what has nowhere else to live, is the distance between what Ptolemy wrote and what his name is attached to.
Six of the twelve places, and six silences
This site covers the twelve houses one entry at a time, and each of the twelve was written against the same chapter: book III chapter 10, on length of life. Read twelve times over, that chapter says something none of the twelve entries can say on its own.
Ptolemy names six places and does not name the other six.
Named, in his own running text: the horoscope, the ascendant, which is his single most-used technical term and the base point nearly every procedure in the book measures from; the Occident, the seventh; the House of the God, theos, the ninth, meaning the Sun; the mid-heaven, mesouranēma, the tenth, which he uses more than any other place-name; the House of the Good Daemon, agathos daimōn, the eleventh; and the House of the Evil Daemon, kakos daimōn, the twelfth 3 bk. III ch. 10.
Unnamed there: the second, third, fourth, fifth, sixth and eighth. His chapter on parents does not proceed by house at all, and his chapter on brothers and sisters uses no numbered third 3 bk. III ch. 10.
Established
The six he names are the six his technique needs. Five of them are prorogative places, the candidates from which the length-of-life calculation may begin, and the sixth, the twelfth, is named in order to be excluded from that same list: the sign that rose before the ascendant is not fit to consider, he writes, being in decline. So his house vocabulary is the working vocabulary of one procedure, and the places it omits are omitted because that procedure has no use for them.
The twelve-place scheme is routinely presented as Ptolemaic. The scheme is older and wider than he is: a conventional set of Greek names for all twelve circulated among practitioners and survives in a papyrus horoscope 3 bk. III ch. 10. Ptolemy reaches into it, takes the six a technique requires, and leaves the rest. Where this site can say what a place signified, it is usually not Ptolemy saying it; see Dorotheus of Sidon, whose ranking covers all twelve.
The same man wrote the astronomy
It is a commonplace that the ancient world did not separate astronomy from astrology, and Ptolemy is where that stops being a generalisation. The two chapters of the Almagest that establish precession are the work of the author of the Tetrabiblos 4 bk. VII chs. 2-3, and this site uses both: the astronomy at Precession of the Equinoxes, the astrology throughout.
The consequence matters for how Three Reference Frames reads. Ptolemy knew precession, adopted Hipparchus’s rate for it, and defined his zodiac from the equinoctial and solstitial points anyway. That was a choice made with the relevant fact in hand, which is the single most misunderstood thing about the tropical zodiac.
The name, and what travels under it
Correction
Commonly saidA table labelled Ptolemaic reports what Ptolemy printed.
Often it does not. The clearest documented case is the dignity material, where several rows shipped by modern software under his name descend instead from Lilly’s 1647 handbook and the sixteenth-century editions behind it. That case is set out with its evidence at William Lilly, and this entry does not repeat it.
The general shape recurs. Ptolemy’s name was the most authoritative available for fourteen centuries, which made it the natural label for material whose actual source was closer to hand and less impressive. Nothing about that requires anyone to have lied. It requires only that a label be more durable than the thing it labels, which labels usually are.
The practical rule this site follows: a claim is Ptolemy’s when it is cited to a book and chapter of an edition named in the bibliography, and not otherwise. That is why every citation to him on this site carries a locus, and why The Tetrabiblos insists the edition be named as well; the chapter numbers differ between them.
References
- Claudius Ptolemy, trans. F. E. Robbins. Tetrabiblos. Loeb Classical Library 435. Cambridge, MA: Harvard University Press, 1940 (composed c. 150 CE). bk. III ch. 10. 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, trans. G. J. Toomer. Ptolemy's Almagest. London: Duckworth, 1984 (composed c. 150 CE). bk. VII chs. 2-3. find a copy (catalogue search) recordprimary source
Reissued by Princeton University Press, 1998. Book VII chapters 2-3 for precession.
- 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 I: The Ancient and Classical Worlds: Continuum, 2009. ISBN 9781441127372 recordscholarly
The standard single narrative survey. Volume I first appeared as The Dawn of Astrology, Hambledon Continuum, 2008. The subtitle is "The Ancient and Classical Worlds", not "The Ancient World"; the shortened form is widely miscited.