Source: The Astrology Encyclopedia by James R. Lewis Visible Ink Press, Detroit MI, 1994
According to Holden, the notion of a belt of zodiacal signs that modify planetary influences according to the sign in which planets are placed originated over 2,500 years ago in the ancient Near East. At least 300 more years passed before the notion of houses was developed, probably by the Egyptian astrologer Petosiris in the mid-second century B.C.E. The earliest house system, which was the system put forward by Ptolemy, was an equal house system.
An equal house system, as the name implies, draws all houses equal in width with respect to the ecliptic (the great circle at the center of the belt of the zodiac). Most systems of equal houses, including the earliest, begin with the first house on the eastern horizon. Thus, someone born when the eastern horizon intersected Virgo at 26 degrees would have a first house that began at 26 degrees Virgo, a second house that began at 26 degrees Libra, a third house that began at 26 degrees Scorpio, and so forth. It is an ancient system of house division that is still used in Vedic astrology, although most Vedic astrologers use the full 30-degree arc of the rising sign as the first house. In other words, if someone’s rising sign was Leo – whether 1 degree Leo, 29 degrees Leo, or any point in between – the full 30-degree arc of Leo from 0 degrees to 30 degrees Leo would be the first house. Then the full 30-degree arc of the next sign – in this example, Virgo – would be the second house, and so forth through the natural order of the zodiac. The most ancient house system used in Western astrology was the same – whole sign – approach to houses as Vedic astrology.
For the most part, the equal house system has passed out of circulation among Western astrologers until relatively recently. Several popular astrology books, particularly Derek and Julia Parker’s The Compleat Astrologer (first published in the United States in 1971), propagated the equal house system because it is the easiest system to use. The increasing popularity of Vedic astrology in the West in combination with the new interest in recovering Western traditional astrology has also helped the older whole sign house system make a comeback. Most contemporary astrologers who do not use the equal house system are severely critical of it.
The other house systems that enjoy widespread acceptance begin the tenth house at the degree of the zodiac that is highest in the heavens (termed the midheaven or Medium Coeli [MC]), and the fourth house exactly 180 degrees away from the cusp (beginning) of the tenth house (termed the nadir). Because of the tilt of the Earth’s axis and the resulting inclination of the belt of the zodiac at a 23-degree angle (the angle of obliquity) away from the plane of the Earth’s rotation, the highest degree of the zodiac for any given point on Earth is often not 90 degrees along the ecliptic from the zodiacal degree on the eastern horizon, even though the zenith and the horizon do, of course, lie at a 90-degree angle to each other. This is difficult to understand unless one is familiar with spherical geometry. Suffice it to say that the substantial angle between the zodiacal belt and the plane of Earth’s rotation results in either lengthening or shortening zodiacal degrees when the zodiac is superimposed on the plane of the horizon and the zenith.
Other than the equal house system, the systems of house division in popular use now all take the axis of the eastern and western horizon as demarcating the cusps of the first house (east) and the seventh house (west), and the axis of the Medium Coeli and the nadir as demarcating the beginnings of the tenth house (MC) and the fourth house (nadir). These systems differ in the various approaches they take to determining the other eight house cusps. Precisely how they differ is hard to explain unless one has thoroughly grasped all the notions related to the celestial sphere and celestial coordinates. The following brief summaries are provided in lieu of elaborately detailed explanations:
- Porphyry Houses: The second-oldest house system was devised by the third-century astrologer Porphyry. The positions of the house cusps for the second, third, fifth, sixth, eighth, ninth, eleventh, and twelfth house are determined by dividing the arcs of the ecliptic contained in the four quadrants of a chart into even divisions of three. Few contemporary astrologers use this system.
- Campanus Houses: Devised by Johannes Campanus, a thirteenth-century mathematician who was also chaplain to Pope Urban IV. Roughly similar to the Porphyry system, except that Campanus trisected the prime vertical in each quadrant, rather than the ecliptic. This system has enjoyed a modest revival because it was the system favored by the influential modern astrologer Dane Rudhyar.
- Regiomontanus Houses: In the century after Campanus, Johannes Muller (who wrote under the name Regiomontanus), a professor of astronomy at Vienna, developed a similar system that trisected the celestial equator. Few contemporary astrologers use this system.
- Placidian Houses: A seventeenth-century Italian monk and professor of mathematics named Placidus de Tito developed this system by trisecting the time it takes a degree of the zodiac to rise from the eastern horizon to the midheaven. Due to the widespread availability of Placidian tables of houses, this was the most popular house system in the early twentieth century, and it still enjoys widespread use.
- Koch Houses: this is a very recent system put forward in 1971 by Walter Koch, that also works by trisecting time. Although Holden characterizes it as possibly the least acceptable of all the time systems, it has enjoyed a surge of popularity over the past decade or so.
Although this overabundance of competing house systems may seem overwhelming, there are numerous other systems, of both ancient and modern origin, that have not been mentioned. These include, among others, Albategnian houses, Alcabitian houses, horizontal houses, meridian houses, morinus houses, and topocentric houses.
Because the differences between the various systems that share the midheaven-nadir axis as the cusps of the tenth and fourth houses are comparatively small, the most significant disagreement between competing popular house systems lies in the divergence between these midheaven-nadir systems and the equal house system. Thus, any attempt to find the ‘best’ system should begin with an examination of this disagreement.
The chief argument in favor of midheaven-nadir approaches is that much informal astrological research has found that the midheaven is a sensitive point in a natal chart for career matters, whereas the nadir is sensitive to matters having to do with house and home. Because these correspond with the traditional meanings of the tenth and fourth houses, it seems inescapable that the midheaven and the nadir should be utilized as the cusps of these houses.
One encounters problems with midheaven-nadir houses, however, when attempting to construct charts for high latitudes. Using any of these systems at high latitudes can result in exaggeratedly large houses (encompassing arcs of over 60 degrees) as well as extremely tiny ones (less than 10 degrees). Thus, in a location like Fairbanks, Alaska, for example, it is unlikely that one would find professional astrologers using anything other than the equal house system as their primary system. Any serious consideration of the problem of high-latitude chart casting seems to present an incontrovertible argument in favor of some kind of equal house approach.
These competing considerations suggest that any house system capable of becoming universally accepted among astrologers must somehow integrate the longstanding astrological experience that stands behind the use of the midheaven-nadir axis for the tenth- and fourth-house cusps with the need to produce houses of reasonable width for individuals born in high latitudes. The basic incompatibility of these two requirements makes the likelihood of resolving the problem of competing house systems highly unlikely in the foreseeable future.