Traditional Term Systems
A term system answers a precise question: which planet rules this degree as its bound lord? Different systems can return different planets, so “using terms” is not a complete method statement. The astrologer must also name the table.
All of the principal traditional schemes divide a sign into unequal planetary territories. The disagreement lies in the order of the rulers, the size of their territories, and the rationale offered for those assignments.
The three names are not equally secure
| System | What survives | Best-supported use | Main caution |
|---|---|---|---|
| Egyptian | A full table used in Hellenistic material, including Valens, and transmitted through later practice | General work with Hellenistic, medieval, and early modern techniques | Manuscript and editorial variants still need to be labeled |
| Ptolemaic | Ptolemy's discussion and alternative distribution in Tetrabiblos I.20 | Work grounded specifically in Ptolemy's astrological framework | It should not be silently substituted for the more widely used Egyptian table |
| Chaldean | An ancient attribution and descriptions discussed through later witnesses | Historical comparison of term doctrine | The label does not identify one uniformly transmitted practical table |
Egyptian terms
The Egyptian terms have the strongest record as a working system. Valens lists their unequal spans and uses bound rulers in interpretation and timing. Their later appearance in dignity tables, including those familiar from William Lilly, helped make this arrangement the usual modern default.
“Egyptian” is a traditional name, not a secure statement about the table's date or inventor. The scheme predates the surviving authors who report it, but the evidence does not permit a simple origin story. It is safer to speak of a received Egyptian arrangement than to claim that a particular priesthood, school, or period created it.
Ptolemaic terms
Ptolemy did not accept every feature of the received material. In Tetrabiblos, he reviews term doctrine and presents a distribution he regards as better grounded in planetary relationships and the structure of the zodiac. The resulting table keeps the basic form—five unequal planetary bounds in each sign—while moving many boundaries and rulers.
The Ptolemaic table is therefore more than a minor spelling variant. Near a changed boundary, it can alter which planet receives term dignity and which planet rules a period in a bound-based timing method. Its clearest use is in a consistently Ptolemaic analysis. Ptolemy's prestige alone is not evidence that later practitioners abandoned the Egyptian arrangement.
The Chaldean attribution
“Chaldean” was an authoritative cultural label in Greek and later astrological writing, but the historical evidence attached to Chaldean terms is less straightforward. Modern summaries sometimes present a clean third table beside the Egyptian and Ptolemaic systems, creating an impression of equal documentary status. The surviving transmission does not justify that symmetry.
When a software program or modern book offers “Chaldean terms,” check which text or edition supplies the values. Without that citation, the name cannot tell the reader whether the table is an ancient witness, a reconstruction, or a later convention. Holden and Brennan are useful guides to the broader transmission problem, but neither historical synthesis turns an uncertain attribution into a universally agreed table.
Why system choice changes the reading
Consider a planet close to a boundary. In the Egyptian arrangement preserved by Valens, the opening bounds of Aries are Jupiter 0°–6° and Venus 6°–12°. Another system may place a different ruler or endpoint there. The change can affect:
- whether the planet is in its own bound;
- whether another planet receives it by term in a method that recognizes that form of reception;
- the dignity points assigned in a medieval or early modern scoring scheme;
- the ruler and duration of a period in a direction through the bounds.
None of these differences proves one table correct. They show why mixing tables within one judgment creates a methodological problem.
A defensible working rule
Use the Egyptian system when reproducing a technique from Valens or from a later author who prints that table. Use the Ptolemaic system when following Ptolemy's own framework. Treat a Chaldean table as edition-specific evidence and cite it accordingly. In every case, record both the system and the source of its degree values.
The Term History page follows the transmission in chronological order. The Term Tables page provides a labeled Egyptian reference rather than blending the systems.