A good understanding and choice of a house system, based on how relevant and reliable it is, are some of the first questions and major preoccupations of an astrologer, because this choice becomes a fundamental part of their interpretations.
In order to understand the different house systems it is also necessary to understand what the astrological Houses are, the establishment of which is their ultimate aim.
House systems, also known domifications, are the different methods, both spatial and temporal, that allow for the establishment of the house cusps.
The terms “house system” and “domification” are essentially synonymous, though domification may also refer to a specific example of this division into houses, not just a set of rules for the division, and today the word domification is much less frequently used.
Producing a domification involves graphically orienting the Earth in relation to the Sun in an exact way.
I will not go into the details of the calculations here, nor will I write in detail about all of the different house systems that exist (Campanus, Regiomontanus, Koch, etc.), not because this is not interesting, but because it would require me to write an entire book, and I invite any interested readers to do some research on this subject.
I will settle here for putting forward the 2 house systems that I use consistently, on this website and in my work, by briefly expounding each of them, one that is more “traditional” and one that is more “modern,” each with advantages and disadvantages :
- the Placidus house system, temporal, dating back to the 17th century
- the equal house system anchored at the Ascendant, spatial, traditional
The more “recent” methods are the result of a heavier use of mathematics, often at the cost of symbolism and traditional analogical comparisons.
The Placidus House System
The name of this system comes from Placido de Titi, known as Placidus, an Italian astronomer, astrologer, and mathematician of the XVIIth century.
Placidus is a temporal house system that rests on mathematical calculations. It is based on the arcs of ascension formed by the planets, from when they rise to when they set, by dividing this ascension at the point of culmination : the Midheaven is considered to be astronomically definitive. It next divides the diurnal arc into sections based on the time that the planets take to ascend further above the horizon in sidereal time.
The Placidus domification thus changes as much as a function of the tilt of the earth at a person’s birth, and thus as a function of the seasons, as it does as a function of latitude.
The advantage of the Placidus house system, thanks to how it is calculated, is that it allows for a nice personalization in the establishment of the astrological Houses for each person.
Thus, when using Placidus, the different sectors of life do not all have the same level of importance for every person, since the sizes of the houses vary…
So what should we think about a small house that contains a cluster of planets ?
Could we come to believe that even a small house is actually strengthened when it is highlighted in a significant way, for example by important transits or a focal point ?
This small house may not be in the foreground of a person’s consciousness, but it may nevertheless have a major influence in their life.
Clearly, the interpretation of a birth chart has many nuances, and the difficulty of interpreting a Placidus domification lies in not falling into these “traps.”
Because of the difference in sizes between the houses, the Placidus house system accentuates the axes, such that they may also be relevant to study specifically. Furthermore, when using the Placidus house system (or other house systems with unequal houses), it makes sense, in the interest of being more exact, to make the orbs of the Aspects in different houses depend on the sizes of the houses in the horoscope. They should therefore be adjusted based on the standard of a 30° house : reduced in size if the house is smaller and increased in size if the house is larger.
This house system also creates what we call Interceptions (intercepted Signs and Planets, along with the houses that are linked).
Thus a temporal domification effectively delivers the notions of cycle and rhythm that are dear to modern humanistic astrologers.
The disadvantage is that we need to know the person’s exact time of birth, without any doubt (see Exactness of time of birth): otherwise, why would we bother seeking out such extreme personalization of the domification ?
What’s more, this house system is much less relevant for people who are born at very high or very low latitudes on the Earth, for whom the houses are often completely “squashed.”
In addition, we partially lose the analogy of the Houses and the zodiac; people reproach Placidus system for being too focused on calculations and the “terrestrial globe” rather than on Man himself (see below the use of the equal house system).
I find the Placidus house system to be reliable in most cases, which is why I have held onto it for my everyday work.
Nevertheless, I regularly use it in combination with the equal house system anchored at the ascendant.
Equal house system anchored at the Ascendant
There are “trends” in astrology, like in anything else, and these days it seems to be in good taste to criticize this equal house system, though this is mostly in relation to Traditional astrology because it was the only system used in the Classical era… but I still do not understand the arguments of these critics.
The equal house system anchored at the ascendant is a spatial domification that divides the diurnal and nocturnal hemispheres each into six equal houses of 30°, starting with the cusp of the Ascendant. This is a bit like the Zodiac signs, which are based on 30° portions of the zodiaca belt (which follows the Earth’s orbit) starting at the vernal point of the spring equinox as 0° of Aries (even though this part of the belt also corresponds to a temporal arc of the orbital period around the Sun, approximately 365 days / 12).
With these houses we get a sort of second zodiac, called the “zodiac of man” (as opposed to the universal zodiac of Signs), which is based on time and is a function of the division of Earth’s rotation over the course of one day (24 hours / 12 = about 2 hours per house).
This idea of having a “second zodiac” corresponds perfectly with symbolism and analogies of the astrological Houses. It allows for a “cross” between this interpretation and the classical “zodiac of signs” in an egalitarian way (namely by giving each one an equal symbolic importance based on an equivalent geometric division, rather than having speculative mathematical calculations that differ between house systems).
To put it plainly, if the “individual zodiac of houses” is to be a reflection of the “universal zodiac of signs,” then it must also have an equal division into 30° segments.
The choice of having the starting point be the Ascendant emphasizes the axis of the horizon with the Descendant (some people prefer to emphasize the Midheaven as a starting point, while still others place the ascendant and the cusps in the middle of the houses).
A spatial division into houses of equal size also has a kind of empirical logic : since human life is really the most important thing, why diminish or emphasize some of its elements by giving them more or less space ?
The human psyche, like the “human body,” remains an essential “human principal.” Even if a person were born without an arm, are they any less human ? Should we “reduce” a single part, a single fraction of their humanity ? Should we grant more or less psychological importance to any particular domain ? To any particular sector of the sky ?
Why not grant equal importance to each element of a human life and to all that it can represent in its wealth of possibilities ?
Quite evidently, using the equal house system is useful for objective psychological interpretation.
Some traditional mystic authors also see in this system the manifestation of a person’s “aura” in its regular form, as it should be.
As for the Zodiac signs, for which we express some fraction of each sign to varying degrees depending on the various dominant factors (Planets, Rulerships, Astrological Elements, etc.), the universal zodiac is not based on a temporal foundation having to do with the eccentricity of the Earth’s orbit, for example, nor is it based on the physical reality of the constellations from which the signs got their names (see my article on the different Zodiacs).
An analysis of equal houses uses exactly the same logic of emphasis (or of Emptiness) as for the signs.
There is a symbolic aspect of this house system that is important to take into consideration when using it : the equal houses anchored at the Ascendant fundamentally represent “perpendicularity”, the incarnation cross, the zenith-nadir axis which is perpendicular to the horizon, and transcendence (do not confuse the zenith and the nadir, which form a kind of perpendicularity with the center of the earth, with the Midheaven and the Imum Coeli, which mark the culmination of the Sun as it rises into the sky at noon and its opposite at midnight). When we lift our eyes to the sky, are we looking at the zenith or the Midheaven ? In this case, they symbolically occupy the same space (even though these two points are still distinct).
One considerable advantage of this domification is its simplicity.
If there are doubts about a person’s time of birth and that the personalized nature of a temporal house system like Placidus is no longer useful, this spatial, equal house system is the best one to use (for example, in a solar chart the equal houses become the “solar houses”).
In reality, the most important point to determine here is the starting point of the houses : the ascendant, the midheaven, the middle of the houses, the Sun, the Moon… each one has its supporters and its critics! Each starting point gives rise to different subtleties in the analysis that follows.
As for my personal experience, I have seen some very interesting results with this house system in a great many birth charts; the simplicity of using it for analysis (I love simplicity !), its symbolism and analogies, and its inclusiveness and fullness, as mentioned above, make it very useful in my opinion.
The alternative house systems of Campanus and Regiomontanus ?
These house systems are spatial, which is what attracted Dane Rudhyar to them : he was a fervent supporter of Campanus and believed that the spatial character of a house system was extremely important (unfortunately, he completely rejected the ancient equal house system, which is one of the only instances where I disagree with his teachings 🙂 ).
The differences between these two domifications are not always very clear, but it may still be useful to analyze them in some cases.
The ancient triple house system
Just a word about the ancient triple house system : this domification uses a combination of the houses of the horoscope (anchored by the Ascendant), the solar houses (anchored by the Sun), and the lunar houses (anchored by the Moon).
This method, although it is longer, gives surprising results.
The technique used here is reminiscent of the one used for “derivative houses”.
Conclusion on house systems
In all birth charts, I consistently use a mix of the equal house system anchored at the Ascendant with the Placidus system. I encourage you to try this method yourself.
Although they seem somewhat contradictory, these two domifications are complimentary. It is worthwhile to observe and study the changes in a birth chart when moving from one house system to the other.
The Placidus house system is especially helpful for situating and studying the meridian : the axis of the Midheaven / Imum Coeli. The locations of the various intermediate houses may give additional information for interpretations, especially for predictive astrology (using Transits and Progressions as well as Interceptions).
In Synastry, I like using equal houses for their clarity and their objectivity in the context of psychological interpretation.
I know that the debate among astrologers is not over, with many of them preferring to use Placidus exclusively because it fosters the idea of a cycle and because it is the most widely used and the easiest to access in tables of Houses, thus avoiding misunderstandings, for example when putting together different charts created by different astrologers (Placidus is an old system, and many astrologers have learned astrology with only this system as a foundation), but are these reasons enough to rule out all other domifications ?
I am just hoping to move towards, with those who are willing, some sort of restitution of the equal house system anchored at the Ascendant. 🙂
It should be noted that, for purists who consider the cusps of a domification to be strictly limiting barriers, the astrologer Ptolemy recommended the use of a “floating system,” granting an orb of a few degrees for each house (the houses began 5° earlier). I find it useful to keep this system in the back of my head : astrology is a dynamic system where the rules should not be set in stone.
It is also best to keep in mind the method of astrological Framing, which can apply as much to the cusps of the Houses as it does to the Planets and may explain certain “zones of influence” in the birth chart which sometimes stretch across multiple houses.
Moreover, in the ancient system, the middle of the houses was considered to be more important than the edges of the houses (the cusps). The sign that occupied the middle of a house was considered its primary ruler.
In short, there is nothing worst for a professional astrologer than using a house system without understanding it and without truly understanding the why behind it, without using skills of critical analysis, and without worrying about the implications that will impact their interpretations. Even though in the end everyone can draw their own conclusions, it is still necessary to give thought to your choice of domification.