Almost everyone who has read the description of their sign has had the same feeling: it is half right. There is a structural reason for that, and it is more than two thousand years old.
Thirty degrees divided into three
The zodiac circle has 360 degrees shared between twelve signs, so each sign occupies thirty degrees. Those thirty degrees are not treated as one homogeneous block: they divide into three stretches of ten, and each stretch is called a decan.
- First decan: degrees 0 to 10 of the sign
- Second decan: degrees 10 to 20
- Third decan: degrees 20 to 30
Twelve signs times three stretches give thirty-six decans. And that is the first answer to why the general description fails: someone born in the first decan of a sign and someone born in the third share a label and little else. Between the two there are twenty degrees, which is more than separates many neighbouring signs.
Each stretch has its ruler
What turns this into a system rather than a mere division is that each decan carries an associated ruling planet. There are two classical ways of assigning it, and it is worth knowing both exist because sources mix one with the other without warning:
- The Chaldean sequence. The seven traditional planets are run through in a fixed order, decan after decan, all the way round the zodiac. It is a purely sequential mechanism.
- By triplicity. The three decans of a sign are shared among the rulers of the three signs of its own element. So the first decan is ruled by the sign itself and the other two by its siblings in element.
The two systems give different results for the same degree. It is nobody's mistake: they are different traditions that survived in parallel. What is a mistake is using one and citing the authority of the other.
And there is a finer division still
Below the decan are the terms, sometimes called bounds: a division of each sign into five unequal stretches, also assigned to planets. It is the finest and most forgotten table of the classical system, and the one that appears least on popular astrology sites, precisely because it does not reduce to a single sentence.
That the stretches are unequal is the interesting part: it indicates the table did not come from a tidy geometric split but from a tradition handed down by copying over centuries.
Why this is not a predictive science
It is worth saying without hedging, because it changes how everything above gets used. Signs, decans and terms are a symbolic language: an ancient and very finely tuned way of naming temperaments, tensions and cycles. They are useful as a vocabulary for looking at yourself, as any well-built typology is.
They do not announce future events, they diagnose nothing and they do not replace a doctor or a psychologist. Anyone selling you the opposite is selling you something else.
The other reason your sign fails
Besides the decan there is a second cause, and it is simpler: the popular description of a sign refers only to the position of the Sun. That is one datum among several. Reducing a whole chart to that single element is like describing a book by its first word.
A note on the ages
Because the Earth's axis wobbles very slowly, the reference point shifts by about one degree every seventy-two years. That is where the so-called «ages» come from, and where the periodic argument about whether the signs «have moved» comes from too. The answer depends on which zodiac is being used, and both positions are internally consistent.
Where all this comes from
- The sequence of the decans, the dignities and the Egyptian terms have been handed down in writing for more than two millennia in works in the public domain, and belong to no one.
- The precession figures are astronomical and verifiable.
This article does not rest on official sources but on common tradition and the public domain: material handed down in writing for centuries and belonging to no one. The writing, the selection and the order are our own work.
This is a summary. The complete table of the thirty-six decans with their ruler, the four essential dignities with the exact degree of each exaltation and the sixty Egyptian terms do not fit in an article. It is in the Zodiacal Codex, a 144-page PDF in Spanish, English and French.
Published by VILLUMINATIONS. The astrology practised here is a symbolic language, not a predictive science: nothing said in it announces future events or replaces the care of a health professional.
