What it is
Essential dignity asks one plain question: is a planet at home in the part of the zodiac it occupies, or a stranger there? A planet in its own quarter acts freely and to its own nature; a planet in hostile ground is cramped, and gives a weaker, more compromised account of itself.
The tradition grades this "at-homeness" by five essential dignities, in descending strength: domicile (the sign a planet owns and rules), exaltation (a sign where it is honoured as an exalted guest), triplicity (rulership shared over one of the four elements), term (a narrow band of degrees within a sign), and face (a ten-degree third of a sign, the weakest tie). Against these stand two debilities: detriment, the sign directly opposite a planet's domicile, and fall, the sign opposite its exaltation. A planet with no dignity whatever in its degree is called peregrine, a wanderer with no title to the land it stands on.
These dignities belong to the degree, not to the chart: they depend only on where a planet sits by longitude, so any planet in the same degree carries the same essential standing in every chart. What varies from birth to birth is accidental dignity, the separate reckoning of house, angle, and solar phase.
How the tradition computes it
Each planet owns two domiciles (the luminaries one each), given in Ptolemy's list of the houses of the planets (Tetrabiblos I.20): Sun in Leo, Moon in Cancer, Mercury in Gemini and Virgo, Venus in Taurus and Libra, Mars in Aries and Scorpio, Jupiter in Sagittarius and Pisces, Saturn in Capricorn and Aquarius. The detriment is simply the sign opposite a domicile.
The exaltations (Tetrabiblos I.22) each fall at a fixed degree, the point of greatest honour, and the fall lies at the opposing degree:
| Planet | Exalted in | Degree |
|---|---|---|
| Sun | Aries | 19° |
| Moon | Taurus | 3° |
| Mercury | Virgo | 15° |
| Venus | Pisces | 27° |
| Mars | Capricorn | 28° |
| Jupiter | Cancer | 15° |
| Saturn | Libra | 21° |
Triplicity follows the two-ruler Ptolemaic scheme (Tetrabiblos I.21): each element has a day lord and a night lord, and the one that matches the chart's sect holds the rulership. Fire is ruled by the Sun by day and Jupiter by night; earth by Venus by day and the Moon by night; air by Saturn by day and Mercury by night; water by Venus by day and the Moon by night. Terms divide each sign into five unequal bands, each with a planetary ruler among the five non-luminaries; the app uses the Egyptian bounds (Tetrabiblos I.23) by default, the scheme Ptolemy himself reports. Faces split each sign into three ten-degree decans, assigned in the Chaldean planetary order; this is the faintest dignity and the app prints no chapter pin for it.
To weigh these against one another the app applies the medieval point scale, additive across every dignity a planet holds:
Domicile +5 Exaltation +4 Triplicity +3 Term +2 Face +1 Detriment −5 Fall −4
One qualification governs the debilities. A planet in its own detriment or fall does not pick up the two weak dignities, term and face, which would otherwise soften a bad placement toward zero. A substantial triplicity of +3 does still count, so a planet in detriment that also rules its element by triplicity nets −5 + 3 = −2 rather than a clean −5. The app reserves the word chariot for a planet standing in both its own domicile and its own exaltation at once. The almuten, or oikodespotes, of any degree is, in outline, the planet that gathers the most dignity over that point; it is taken to be the lord of the place.
What it signifies
Dignity is read in physical-causal terms, as the strength with which a planet can pour out its own nature. A planet in domicile or exaltation has full command of its qualities: the hot and moist good of Jupiter, or the cold and dry harm of Saturn, comes through cleanly and to full measure. Its significations, whether kindly or hurtful, are delivered.
A planet in detriment or fall is thrown out of its temperament, so that even a benefic gives a thin, obstructed good, and a malefic works its harm crookedly and without command of itself. The peregrine planet, holding no title, acts without steadiness and readily takes on the nature of whatever aspects it. The point scale simply totals these balances of strength and weakness into one figure per planet, so the reader can see at a glance which bodies are fit to act and which are compromised.
Where the app departs
Where the app departs
The additive numbers are not Ptolemy's. Ptolemy ranks the dignities in order of strength but assigns no point values to them at all. The +5 to +1 weighting, and the −5 and −4 for the debilities, are the later medieval convention set out by William Lilly (Christian Astrology, 1647), after al-Biruni and the Arabic tradition. The assignments the app uses, which planet rules which sign, degree, triplicity, term, and face, are genuinely Ptolemy's; only the numeric weighting is medieval.
The app also defines chariot more narrowly than Ptolemy did, restricting it to a planet in both its domicile and its exaltation. Ptolemy counts a planet as being in its chariot when it holds the place it occupies by any two or more of the five modes of dignity. The app labels its narrower rule as its own convention, not as Ptolemy's.
Seen in a real chart
Marcus Aurelius, born shortly before dawn at Rome on 26 April 121 CE, gives a nocturnal chart with Pisces rising. Reading the seven planets by essential dignity alone, the app returns:
| Planet | Sign | Dignity | Score |
|---|---|---|---|
| Sun | Taurus | Peregrine | 0 |
| Moon | Capricorn | Detriment | −2 |
| Mercury | Taurus | Peregrine | 0 |
| Venus | Pisces | Exaltation | +4 |
| Mars | Taurus | Detriment | −5 |
| Jupiter | Scorpio | Term | +2 |
| Saturn | Cancer | Detriment | −5 |
The strongest body is Venus, exalted in Pisces at +4, which the engine also elects as the chart lord. The Moon shows the debility-dominant rule at work: in Capricorn she stands in her detriment, opposite her domicile of Cancer, for −5, but Capricorn is an earth sign, and by night the Moon rules the earth triplicity, so a substantial +3 survives the debility while the weak term and face are suppressed. The net is −5 + 3 = −2. Mars and Saturn, both in detriment with no triplicity to lift them, read a clean −5 each, while the Sun and Mercury in Taurus are peregrine, holding no title at all.
How to read it in the app
In a natal reading the dignity of each planet is printed in the chart's dignity table beside its sign and score, with the chart lord named from the totals. The state-key footnote there discloses the point scale's true provenance, that the assignments are Ptolemy's while the numbers follow Lilly and the medieval tradition, so the reader can see which part of the figure is ancient and which is later convention.
Sources
Tetrabiblos I.20, "Houses of the Planets" (domiciles). Ptolemy, trans. J. M. Ashmand, London, 1822.
Tetrabiblos I.21, "The Triplicities" (two-ruler triplicity by sect). Ashmand, 1822.
Tetrabiblos I.22, "Exaltations" (exaltation degrees and falls). Ashmand, 1822.
Tetrabiblos I.23, "The Disposition of the Terms" (the Egyptian bounds the app uses). Ashmand, 1822.
Faces (decans) are given in Ptolemy, Book I; the app prints no chapter ornament for them and none is cited here.
Point scale after William Lilly, Christian Astrology, London, 1647, following al-Biruni and the Arabic tradition; not a Tetrabiblos doctrine.