Essential Dignity
Essential dignity is how well a planet is placed in the zodiac itself — by rulership, exaltation, triplicity, term or face. It measures a planet's capacity to deliver on what the chart has already promised. It isn't a measure of whether the planet is good or bad.
The fuller picture
There are five essential dignities, and they're ranked. A planet in the sign it rules is in its domicile, the strongest placement, worth five points. In its sign of exaltation it scores four. Ruling the element of the sign it occupies — fire, earth, air or water — earns three by triplicity. Sitting in one of the five unequal slices each sign is divided into earns two, by term. A face, the weakest, earns one. Two debilities pull the other way: a planet in the sign opposite its own is in detriment, and a planet opposite its exaltation is in fall. Add it all up and each planet has a single number.
What that number means is the part most often got wrong. It isn't a measure of how pleasant a planet is, or of how much the person asking will enjoy what it does. It measures capacity — whether the planet has the resources to carry out what the chart has already promised. Put it the other way round: a well-dignified malefic is a difficult planet that can do exactly what it intends, and a benefic in fall wishes you well and can't help.
The dignities also split into major and minor, and that wording matters more than it looks. Domicile, exaltation and triplicity are major: a planet holding any one of them is straightforwardly essentially dignified. Term and face are minor. A planet resting on those alone is better described as weakly dignified, because the plain word overstates what it can actually do. One working threshold: three points or more, with the planet not in detriment or fall — so triplicity on its own clears it, term and face together clear it, and term alone or face alone doesn't.
The far end has its own name. A planet holding none of the five is peregrine, a wanderer: nothing in that sign answers to it. Dignified and peregrine are two sides of one test rather than two separate judgements, so the only question is ever whether the planet holds at least one dignity — which makes the edge cases worth getting right. They gather around triplicity, because rulership of an element is usually split between a day ruler and a night ruler, and a planet that rules the element by night earns nothing at all in a chart cast by day. A third, participating ruler counts in either. So the same Moon on the same degree of Virgo can be dignified in one chart and peregrine in the next, purely because one question was asked at night.
The term table also quietly explains something the tradition usually asserts without a reason: why the end of a sign is read as unlucky. The final degree of any sign — 29°00′ to 29°59′ — is called anaretic, and roughly the last three degrees of every sign have long been treated as malefic. The reason is structural, and it's checkable. The final term of every sign belongs either to Saturn or to Mars. Not one of the twelve has a benefic in its last term, and that holds in both term tables the tradition uses, the Egyptian and the Ptolemaic. A planet drifting towards the end of a sign is walking into the property of one of the two malefics, whichever sign it happens to be in. Which suggests the sharper way to state the rule: it's less about a particular degree number than about the planet having reached the final term of wherever it sits.
Essential dignity is only half of what makes a planet effective, and taken alone it can mislead badly. The other half is accidental: which of the twelve houses the planet falls in, whether it's moving forward, whether it's lost in the Sun's rays. A planet with every essential dignity going can be placed so badly that it has no way to deliver on any of it — essential strength in the sixth or the twelfth, the two houses that make no aspect at all to the rising degree, buys very little. A planet in its own house of joy gains comfort and familiarity there, which isn't the same thing as strength. The third and ninth are cadent houses too, but they do at least sextile and trine the rising degree, which is one modern traditional practitioner's stated reason for rating them above the sixth and twelfth — a departure from the usual ranking, and offered as one.
In your chart
Every chart in iHorary carries a dignities table: one row per planet, one column per dignity and debility, each cell scored on that five-four-three-two-one scale with a running total, and the planets your question turns on marked out from the rest. Open a planet in the wheel's dossier and it names the dignities that planet holds — or reports it peregrine — alongside its house, its motion and where it stands relative to the Sun. Terms are computed on the Ptolemaic table by default — the bounds Lilly himself prints — and triplicity on Lilly's own two-ruler set; the Egyptian bounds and the Dorothean triplicities are implemented as selectable alternatives, and each pair disagrees about a handful of degrees.
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