Welcome to the third installment of the Astrology 101 series! We’ve previously discussed the twelve zodiac signs and the ten planets (seven visible and three outer). Now we get into the philosophy and the reason why this system is designed the way it is, especially how the planets became assigned rulers to certain signs.

Thema Mundi is a Latin translation of the Greek phrase kosmous genesis, meaning “Nativity of the Cosmos” or “Birth Chart of the World.” It sets the rationale and basis for rulerships and is one of the core concepts of how we interpret charts. This discussion can get very technical, but for our purposes we will focus on the basics.

The Birth Chart of the World

The creation of the Thema Mundi starts with assigning the planets to each sign that they rule, otherwise known as their domicile. Cancer is placed as the rising sign, or the sign that is rising up over the horizon. The Moon is then assigned to Cancer followed by the Sun to Leo, then the rest of the planets are assigned starting with the planet closest to the Sun to the next zodiacal sign in order, Virgo, and so on. The original chart looks a bit like below.

There isn’t a lot of text that has survived about why Cancer was assigned to the rising sign, but astrologers theorize from a text ascribed to Berossus, that it’s possibly due to the fact that Cancer is the start of Summer, the hottest part of the year and the creation of all blooming life. The sign opposite to Cancer, Capricorn is the coldest part of the year and results in the death or hibernation of the all the fruits and animals. Because Cancer is a nocturnal sign, the Moon was assigned to rule it, and as Leo is diurnal, the Sun was assigned to that sign.

Additionally, the Egyptians followed the fixed star Sirius, and when that star would rise in the Summertime the Nile river would flood which marked the beginning of the Egyptian calendar. Sirius would make its first appearance when Cancer was rising over the horizon, therefore assigning Cancer as the starting point for the Thema Mundi.

The other planets were assigned due to the proximity to the Sun. Mercury never gets further than one sign away from the Sun and so it was assigned to Virgo, the next sign after Leo. Venus never gets further than two signs away from the Sun and is therefore assigned to Libra. Mars is the next furthest planet, then Jupiter. Saturn is the furthest and slowest visible planet and is accurately assigned the sign opposite to the Moon, Capricorn.

Understanding Domiciles

The rulership scheme then continues around in zodiacal order. Aquarius is opposite to the Sun, still far away from the original source of light, so Saturn is assigned to that sign. Pisces is next and is moving closer to the beginning, so it gets assigned to Jupiter. Keeping in that order, Mars is next followed by Venus, and then Mercury to Gemini so the zodiacal wheel is complete.

As we saw with the previous posts, many of the planets that rule a sign have similar and complementing characteristics that help color or give that sign meaning. Planets in domicile feel at home, their significations and functions work well in that sign and they can get what they need to be strong and successful.

Simply think of each sign as a physical house. In Capricorn, that house will most likely be cold, but stable and structurally sound. Inside that house, the energy will be focused on work and accomplishing goals or setting rules and boundaries. Saturn inside that house will be happy, as Saturn wants us to focus on the structure, goals, and responsibilities of life. This planet is more focused on work, material matters, and less on emotions or relationships.

Detriments

What happens when a planet is in the sign opposite to its domicile or home? This is known as the detriment of the planet, or where the planet may feel like it’s in exile or an outcast. Returning to our Capricorn example, suppose the Moon enters Capricorn’s house (as it does every month). If you remember from the planetary post, the Moon likes comfort. It’s very much associated with nurturing, caring, sensitivity to our emotions, and inner awareness. In the sign of Capricorn, where work, goals, and physical structures are valued, the Moon will feel uncomfortable.

Instead of being able to attend to her needs by seeking emotional stability, she will be forced to push those needs aside and get to the task at hand, focus on work, and needing to value what is physically present.

It’s important to note that planets in their detriment is not necessarily bad, but it forces the planet to work in a way that is unfamiliar or uncomfortable initially. They have to get creative and accomplish their purpose in a way of the sign that it’s in, which may feel unintuitive and unusual at first. Planets in detriment have to work harder than those in their domicile.

Exaltations and Depressions

On the flip side, there are signs that the planet does extremely well in, even more powerful than in its usual domicile. These are known as exaltations. For a planet to be exalted, it’s said to be at its highest, to be on a throne or crowned and worshipped. Planets that are exalted have more influence and are able to get their significations across more boldly and clearly.

The planets’ exaltations are shown in the chart next. The Moon is exalted in Taurus, the Sun in Aries, Mercury in Virgo, Venus in Pisces, Mars in Capricorn, Jupiter in Cancer, and Saturn in Libra. Additionally, the Hellenistic tradition has specific degrees of exaltation where the energy is at its highest:

· Moon – 3° Taurus

· Sun – 19° Aries

· Mercury – 15° Virgo

· Venus – 27° Pisces

· Mars – 28° Capricorn

· Jupiter – 15° Cancer

· Saturn – 21° Libra

Similar to the domicile/detriment pattern, the sign opposite to the exaltation sign is known as the place of the planet’s fall or depression. Therefore, the Moon is fallen in Scorpio, the Sun in Libra, Mercury in Pisces, Venus in Virgo, Mars in Cancer, Jupiter in Capricorn, and Saturn in Aries.

To be in the fall or depression is similar to the detriment, but a little different. The signs of domicile are known as the planets’ home, where they are the most comfortable because they rule that sign. Detriment signs are places where the planets struggle to find ease or work naturally. When a planet is exalted, they are still a “guest” of the house but is immediately placed into an authority position where they can exalt their power with support. By contrast, when a planet is fallen, they are a guest of a house where they are not welcome, and the environment may even feel hostile. Their significations are diminished as unimportant and irrelevant in that sign, and they have to work extra hard just to be recognized.

Take for example, the exaltation of the Sun in Aries and fall in Libra. The Sun’s signification is to shine and to express oneself without fear or concern. Aries Sun people are often very bold, influential, headstrong, and stubborn about themselves and their beliefs. They are not afraid to say or be what feels authentic to them, even if they are in the minority. In this sign, the Sun’s significations are highly valued and sought after.

Libra Sun people are always more concerned about the other, or the relationship. Their identity and belief of themselves may become wrapped into the identity of the other, and they may have trouble separating true authenticity of themselves or finding who they are outside of the group. As the Sun’s main goal is to shine and be personal, it’s fallen in a sign where relationships are given priority.

Why are these signs assigned as the exaltations? This is beyond the scope of this post, but the rationale is based on aspects — nocturnal planets exaltations are connected through sextiles, and diurnal planets exaltations are connected through trines. We will revisit sextiles and trines in a future Astrology 101 blog post.

Important Note About Planetary Placements

If majority of your natal planets are in detriment or depression, it does not mean your life will be hard or that you will struggle to achieve your goals. It simply means that your approach to life and the way the planets accomplish their significations will be different. This is what makes astrology interesting. Simply because your Mercury is not in Virgo and instead in Pisces does not mean you cannot be a writer or speaker, but the way that you write or speak will be done in a more dreamy, poetic form. Perhaps logical arguments won’t be your forte, but creative communication will be.

Learning about your planetary placements and rulerships is important because it shapes how you move through life and shows how the different archetypes will ultimately manifest. Request a natal chart reading to see how this personally impacts your life here.

Works Cited

Brennan, C. (2017). Hellenistic astrology: The study of fate and fortune (First Edition), 270-293, Amor Fati Publications

Astrology 101: The Thema Mundi