New millennium astrological chart
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Essential dignity, in astrology, refers to the relative strength or weakness of a planet or point's zodiac position by sign and degree, or its essence—what the pre-eminent 17th-century astrologer William Lilly called "the strength, fortitude or debility of the Planets [or] significators." In other words, essential dignity seeks to view the strengths of a planet or point as though it were isolated from other factors in the sky of the natal chart.
By comparison, accidental dignity indicates how much strength a planet or point derives from its position in a natal chart, such as its relation to the other factors in the chart: for example, its proximity to other planets, or to the four angles of the chart, or to stars, as well as the aspects (or symmetrical angular connections) it forms with other planets or points in the chart.
For example, the essential dignity of Mars, if located at 27 degrees of Capricorn would take into account the fact that Mars is exalted in Capricorn, and also that it is the bounds ruler of the 27th degree of Capricorn and also the face ruler of the 27th degree of Capricorn. This is a considerably dignified Mars.
If that Mars were located in the twelfth house of a natal chart Mars's accidental dignity would be poor, since it would be located in a weak or malevolent cadent house. Were Mars to also be squared to a malevolent planet, such as Saturn, and would be receiving a dexter square aspect from malefic Saturn, ruler of Capricorn, this would further hinder Mars's strength and ability to operate benevolently. These accidental dignity factors would tend to weaken a Mars which is otherwise strong in essential dignity.
Traditionally the five essential dignities are:
- Domicile (rulership or house) + detriment
- Exaltation + fall
- Terms (or "bounds")
- Face (or "decan")
For post-Classical astrologers, such as Bonatti or Lilly, the dignities had a hierarchy. The most important dignity was domicile rulership; slightly less important was exaltation. Triplicity rulerships were still fairly important in medieval astrology, but nowhere near as vital as they were for Hellenistic astrologers such as Ptolemy. Terms or bounds rulerships became very much diminished in importance, and face rulers were almost entirely ignored. (Lilly said that the only function face rulers served was to keep a planet from being entirely peregrine—that is, without any essential dignity whatever—which was considered a malefic condition.)
However, Hellenistic astrologers had a very different view of the dignities. To earlier astrologers, such as Ptolemy and Vettius Valens, domicile rulership, exaltation, triplicity rulership and bounds rulership were all of equal strength in influence.
Many modern astrologers take little heed of essential dignities, with the exception of domicile rulerships (see article on ruling planets.) This is most likely the result of the simplification of astrological technique that occurred when astrology lost popularity beginning in the eighteenth century (see History of astrology.)
Table of Faces (or Decanates, Traditional Chaldean)
|Sign||First Decan ruler
(0 - 9.999 deg.)
|Second Decan ruler
(10 - 19.999 deg.)
|Third Decan ruler
(20 - 29.999 deg.)
* as used as an essential dignity in astrology.
Notice that rulerships follow a repeating pattern, the so-called "Chaldaean" order of the planets: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. This planetary order, in which the Sun stands at the center of the continuum, with the planets between the Sun and the Earth on one side and the outer planets on the other side, reflected the perception of the speed of each planet's motion as seen from the Earth.
Decans or "faces" are the least important of the essential dignities, representing about one-fifteenth of a planet's overall strength in medieval astrology.
Table of Faces (or Decanates, Modern Ruler-Ships)
The decans and their rulers are assigned as follows as based on the concepts of Modern Western astrology :
|Sign||1st decan ruler||2nd decan ruler||3rd decan ruler|
In astrology, a decan is the subdivision of a sign. In order to give fuller interpretation to the Zodiac Signs, ancient astrologers subdivided each Sign into periods of approximately ten days. These divisions are known as the "decans" or "decantes" and cover modifications of individual traits, attributed to minor planetary influences, which temper or blend with the ruling influence of the period. The ten-day spans are somewhat arbitrary in order to allow for the five (and sometimes six) extra days in the year beyond the 360 days required for the thirty-six decans. Modern Astrology updates the Ruler-Ships. Decans or "faces" are the least important of the essential dignities, representing about one-fifteenth of a planet's overall strength in medieval astrology, Thus time spent on the other Essential Dignities and perhaps "Astro-dynes" would be better spent. This remains, however a fast and easy way to gain a little further depth in a reading.
[Modern ruler-ships] 
[Chaldean ruler-ships] 
Many modern astrologers, eschewing the use of the other essential dignities, use the three outer planets, Uranus, Neptune and Pluto as the modern rulers of Aquarius, Pisces and Scorpio, respectively. The practice derives from the similarity between the nature of the planets with the nature of these signs. This as illustrated by the differences in the two "decans" tables above.
- William Lilly, Christian Astrology, Book 1: An Introduction to Astrology; 1647. 2nd ed., 1659. Facsimile of 1647 edition by Ascella Publications, ed. D. Houlding, London, 1999, p.101.
- William Lilly, Christian Astrology, Book 1: An Introduction to Astrology; 1647. 2nd ed., 1659. Facsimile of 1647 edition by Ascella Publications, ed. D. Houlding, London, 1999, p. 104. This is perhaps the source referred to most commonly, but the same table will be found in Ptolemy's Tetrabiblos, Valens' Anthologiae, Guido Bonatti's Liber Astronomiae, and a great many other major textbooks and sources.
- William Lilly, Christian Astrology (London, 1647), pp. 104, 105.
- According to Horoscopeswithin.com - http://www.horoscopeswithin.com/decans.php
- According to novareinna.com - "Archived copy". Archived from the original on 2010-01-03. Retrieved 2009-07-23.CS1 maint: Archived copy as title (link)
- Ptolemy, Tetrabiblos, tr. J. Ashmand, 1822, complete. 
- Vettius Valens. The Anthology. Book III. [translated by Robert Schmidt and edited by Robert Hand.] Project Hindsight, Greek Track, Vol. VIII (The Golden Hind Press, Berkeley Springs, WV, 1994).
- Late Classical Astrology: Paulus Alexandrinus and Olympiodorus (with the Scholia of later Latin Commentators). (Translated by Dorian Gieseler Greenbaum.) Archive for the Retrieval of Historical Astrological Texts (ARHAT) , 2001.
- William Lilly, Christian Astrology, Book 1: An Introduction to Astrology; Book 2: The Resolution of All Manner of Questions, 1647. 2nd ed., 1659. Re-published by Astrology Classics (Bel Air, Maryland), 2004; by Ascella Publications, ed. D. Houlding, London, 1999; and [in facsimile of 1647 edition] by Regulus Press, London, 1985.
- William Lilly, Christian Astrology, Book 3: An Easie And Plaine Method Teaching How to Judge upon Nativities, 1647. 2nd ed., 1659. Re-published by Astrology Classics (Bel Air, Maryland), 2004; by Ascella Publications, ed. D. Houlding, London, 2000; and [in facsimile of 1647 edition] by Regulus Press, London, 1985.
- Hand, Robert. Horoscope Symbols. Schiffer Publishing (Easton, PA., 1987), ISBN 0-914918-16-8.
- Crane, Joseph. Astrological Roots: The Hellenistic Legacy. (The Wessex Astrologer, Ltd., 2007.) ISBN 1-902405-24-2.
- Marion D. March and Joan McEvers, The Only Way to Learn Astrology, 6 volumes. (ACS Publications, San Diego, 1982.)
- Understanding Planetary Dignity and Debility, by Deborah Houlding; Skyscript.