Mercury in Astrology: The Myth Astrologers Blew Up

Most people familiar with modern astrology—whether by hearsay, through popular publications, or especially those who have studied it in contemporary astrological schools—know that Mercury is said to govern intellect.

Let’s examine how accurate this widespread belief really is. As an example, I will analyze a natal chart in which Mercury is in conjunction with a debilitated Saturn, which is traditionally considered an unfavorable position for Mercury.

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Modern Interpretation

I conducted a survey among astrologers to find out what exactly this conjunction means. Most agreed that it indicates a slow thinking process.

I also asked what would happen if Saturn's aspect, by transit or direction, were to pass over Mercury and activate the conjunction. The majority of astrologers believed that this would clearly result in cognitive difficulties.

Interpretation Using Renaissance Techniques

I deliberately chose techniques from this historical period because astrology at the time had reached its highest level of development: it was strictly predictive, empirically tested, and taught in leading European universities, such as at the University of Krakow, in the Department of Mathematics and Astrology.

Let’s examine the natal chart through the eyes of a Renaissance astrologer. The first thing that becomes immediately obvious is that Mercury in this chart is not associated with speech, thought, or the intellectual capacity of the native. Here’s why.

Do Planets Always Play Their Natural Roles?

According to the works of Jean-Baptiste Morin (Morinus), a 17th-century professor of mathematics and astrology at the Collège Royal in Paris, a planet can only express its natural qualities if it is determined by the appropriate house in the horoscope.

For example:

• For the Moon to signify children, it must be connected to the fifth house of children;
• For Venus to indicate love, she must be connected with the seventh house of relationships;
• Therefore, for Mercury to signify the native’s intellect, it must be connected to the first house—the house of the native themself.

However, in this chart, Mercury has no connection to the first house:

• It is not located in the first house and does not cast rays through it;
• No sign ruled by Mercury is found within the house, so no rays reflected from these signs pass through the first house either;
• Mercury casts no aspects into the first house—no part of it reaches into the 1st to deliver influence.

Therefore, the first house does not focus Mercury’s rays upon the native. In this chart, Mercury cannot be an indicator of intellect. It represents something else entirely. The question is—what?

Accidental Significance of Mercury

Mercury rules the twelfth house. This house traditionally signifies four things: secret enemies, exile, imprisonment, and illness. To specify which of these four roles Mercury most likely plays, we need to examine which other planets are clearly connected to the 12th house and shape its matters.

Opposite the 12th house is the Moon. According to Morinus, a planet in a house becomes the accidental ruler of the opposite house. Therefore, the Moon becomes the accidental ruler of the 12th house. Moreover, the Moon governs the 1st house, which represents the native’s life as a whole.

This can be read literally—the native’s life path (or at least a significant portion of their life) will be associated with the themes of the 12th house. Now let’s ask—what do the Moon and the 12th house have in common?

The Moon, by analogy, signifies newborn children, sailors, sea creatures, wandering, and the like. What do these meanings have in common with the 12th house? The only logically consistent overlap is wandering or exile. The other combinations make no logical sense.

Therefore, the native’s life path will involve exile. Thus, exile—or forced emigration—is the most evident meaning of the 12th house in this chart. Mercury, as ruler of the twelfth house, most strongly points to this meaning.

Clarifying Mercury’s Role

Note that Mercury is in conjunction with Saturn. If we interpret Mercury as indicating emigration, we find that emigration occurs in connection with Saturn.

Saturn, in turn, rules the eighth house of mortal danger and naturally signifies death. It combines both natural and accidental meanings, and thus indicates lethal threats more strongly than anything else. Therefore, the native’s forced migration will be caused by a threat of death.

Comparison of the Two Schools

Now compare this to the modern interpretation: according to it, the Mercury-Saturn conjunction points to slow thinking, and a Saturn transit or direction to Mercury will bring cognitive difficulties.

The old astrological school says that the native’s life will involve exile, and that a Saturn aspect to Mercury will trigger a real-world event—forced emigration due to a mortal threat.

Fact-Checking

To determine which interpretation is closer to the truth, we will verify the planetary meanings through verifiable life events. To predict the timing, I use the method of primary directions. I take the Saturn aspect as the promissor, and Mercury as the significator of the event. The most interesting direction involves Saturn's aspect at 4° Gemini—this aspect falls on the cusp of the 12th house, meaning it is directly related to the issue under investigation.

This direction points to February 1933. Events typically occur a few months after the direction, so I expect the event to manifest in March–April 1933.

To summarize:

• According to modern astrology, we expect cognitive issues in March–April 1933;
• According to the Renaissance tradition, we expect forced emigration during the same period.

Now let’s turn to the facts. This was Albert Einstein’s horoscope. His thinking was not slowed; on the contrary, he was a genius.

At the end of March 1933, as Nazi “purges” began in Germany and Einstein fell into political disfavor, he renounced his German citizenship, officially informing the Prussian Academy of Sciences on April 5. He left Germany and spent the rest of his life in exile.

There is no evidence that he experienced any cognitive dysfunction, including slowed thinking, in March–April of that year.

As you can see, the modern astrological school fails the fact-check, while Renaissance techniques remain valid and effective to this day.