Firmicus Maternus: A skeptic among the stars

A lawyer turned astrologer turned devout Christian, Firmicus Maternus penned the eight-book Mathesis, one of the lengthiest extant works on Hellenistic astrology in Latin, giving sixteen centuries of readers insight into astrological practices during the Roman Empire.

Published Categorized as History
A busy port city with business and government buildings.
Port of Messina, Sicily, Italy

Julius Firmicus Maternus (c. 280-c.360 A.D.), a retired Sicilian lawyer, was the astrologer that produced one of the lengthiest known textbooks on Hellenistic astrology in Latin. His work, the Mathesis (“the science [of astrology]”), was published in the mid-fourth century A.D. (either 337 or 355 A.D.). 

His work is impressive. He wrote about the fundamentals of the astrological practice, making the Mathesis a particularly valuable textbook—many astrologers of the period, including Ptolemy and Valens, did not explain in their own work because they assumed that the reader already knew the basics. Additionally, he wrote delineations for each of the planets in each of the houses and signs, plus the aspects they could make between themselves. Unfortunately, however, there are some lacunae in various parts of his work.

In this article, we are going to learn more about the life of Firmicus, the importance of the Mathesis, and what its contents offer the practicing astrologer.

The history behind Mathesis

Most of what we know about Firmicus comes from the Mathesis itself and his other work, The Error of The Pagan Religions. He was born and lived in Sicily, where he pursued a career in law. He eventually grew tired of his job and the risks associated with it and retired, pursuing studies in literature and science instead—which included astrology.

In his books, Firmicus refers to himself using the title Vir Clarissimus and Vir Consularis, which indicates that he was a member of the senatorial class. He had, hence, the resources to pursue his studies without any encumbrances. This is also how he became acquainted with the consul Lollianus Mavortius, the person for whom the Mathesis was written. The astrologer tells us a story in the Mathesis about how Mavortius took care of Firmicus after a long, cold journey he had undertaken. After recovering, he and Mavortius spent long hours discussing Sicily and astronomy. Most of the astrological works of that time were written in Greek but Firmicus was apparently familiar with them and, for this reason, promised Mavortius to translate all of that knowledge into Latin.

It took him a lot of time and effort to write all the eight books that compose the Mathesis. Researchers believe he took either seven years or 25 years to finish the book, and Firmicus admits multiple times that it was a difficult endeavor—he even considered giving up at times. Nevertheless, he managed to finish the book that would become one of the main resources for the study of ancient astrology from medieval times until today.

The Mathesis

Each of the eight books of the Mathesis is composed of multiple chapters that explain the fundamentals of astrology, both essential concepts and specific techniques. The first book explains his journey in writing the Mathesis, his history with Mavortius, and analyzes and refutes arguments against astrology.

The second book is about the fundamental concepts of astrology: the signs, the planets, the subdivisions of the zodiac (decans and terms), the houses, the aspects, and some other technical details of relevance to the practicing astrologer, such as the antiscia—the connection between two signs based on how far they are from the solstices. The end of this book has a very interesting admonition to the astrologer regarding how they should conduct their business, what kind of moral code to follow, and what not to do. For example, Maternus warns students not to make predictions about the life of the emperor, which was valuable advice, since during the time of the Roman Empire doing so could lead to imprisonment or execution.

The third book focuses on the Thema Mundi, the chart of the beginning of the universe, and how it was used as a didactic concept by the astrologers that preceded Firmicus. Most of it, however, is about the meaning of each of the planets in each of the houses. There are a lot of specific details in those chapters, such as whether the chart is diurnal or nocturnal, if there are aspects from other planets, and how this would influence the significations of the planet-house combination.

The fourth book is mainly about the Moon and its aspects. This book also explains the Lot of Fortune and the Daemon and how to calculate the ruler of the chart and its meanings. There are some other technical concepts of interest in this book.

Most of the fifth book has, unfortunately, been lost. The remaining chapters are about the positions of the angles in the chart (Ascendant, Descendant, Mid Heaven, and Imum Coeli), the positioning of the Ascendant, and, in the end, something that certainly would cover a lot of information: the significations of each of the planets in each of the twelve signs. Only the positions of Saturn and part of Jupiter have survived.

The sixth book contains information about aspects between the planets and the luminaries (the Sun and the Moon) and also explains how to calculate ‘lots’ of specific themes: the father, the mother, illnesses, etc. This is very fascinating since it was thought for a long time that some of these ‘lots’ were initially created by the Arabs. Many of the ‘lots’ were first described by Firmicus since most ancient authors only used a few lots.

Book seven is very technical, dealing with particular themes in a chart, beginning with charts of infants that were abandoned to die (sadly, a common practice in that cultural context) and ending with the occupations that one would have. Other themes include sexual matters, death, illnesses, and children.

The eighth book is mainly about the fixed stars, including some interpretations. This theme was important for Firmicus and other ancient authors, although its importance has since diminished.

Example Themes

We can glimpse the depth of ancient astrological knowledge by reading the Mathesis. As an example, let’s look at some of the information that Firmicus give us about the Moon and its aspects with other planets. This will allow us to understand what other elements of the natal chart were of main importance in the analysis.

If the waxing Moon is in aspect to Jupiter or is moving toward him, the natives will be fortunate, famous and rich; master of many great estates and wide possessions. (IV.III 1)

But if the waning Moon is in aspect to Jupiter, the natives will be adopted; or exposed, and later returned to their parents. They seek income by their own efforts, and over a period of time receive advancement and achieve power and fame. (IV.III 2)

The difference between these two indications is the Moon phase. Ancient astrologers usually considered the waxing Moon to be more benefic, as it is increasing in light. For the same reason, the waning Moon is not so great and can sometimes act as a malefic. In the aforementioned quotes, since Jupiter is a benefic planet, the difference is about the quality of the life of the native: in one case, he is born with fortune and fame; in the other, he has to struggle to achieve it. 

Not only the aspect is important—one should know if the Moon is approximating to the other planet (“applying”) or separating from it. The approximation appears in the aforementioned quotes, so here is what the separation of the Moon from Jupiter indicates:

If in a nocturnal chart the waxing Moon, moving away from Jupiter, is carried toward Mars, great power is predicted: control of great states and regions. But it also indicates anxieties and dangers. […] (IV.X 1)

But if the waxing Moon is moving away from Jupiter toward Mars by day, the natives will be exposed, be slaves, or wretched beggars. They will suffer illness and afflictions, slavery which is like captivity, and lose their life in a violent death. (IV.X 2)

The waning Moon in this situation wastes paternal and maternal inheritance, destroys the parents when the native is young, and imposes the burden of extreme beggary. (IV.X 4)

When the Moon is separating from one planet, it can be moving towards another. This is important in chart analysis and combines the symbolic meanings of the planets. The Moon separating from Jupiter as it approaches Mars can indicate power or misfortune, depending on other factors.

Besides the importance of the Moon phase, there is the fundamental value of sect: whether the chart is diurnal or nocturnal. Mars is a nocturnal planet and therefore the waxing Moon separating from Jupiter and approaching Mars by night is positive; but by day, it is negative.

The waning Moon is likewise negative and Firmicus does not distinguish the chart sect in this case: only bad predictions are given here. If Jupiter gives good things, Mars tends to waste these gifts and bring suffering; the exception depends on other astrological factors, as we’ve seen before.

These examples show us how the Mathesis is valuable in teaching us the complexity of ancient astrology. The abundance of examples based on the positioning of the planets considering multiple possibilities helps us understand the rationale behind Hellenistic astrology, something that most authors fail to explain clearly.

After the Mathesis: A Christian Firmicus against the Pagans

The second work of Firmicus that has survived to the present day is known as “The Error of the Pagan Religions”. It is estimated to have been written around the year 347 A.D. Since there is some debate about when the Mathesis was finished, it is not known whether Firmicus wrote this work before or after the completion of the Mathesis.

The emphasis in this other work was on attacking Paganism and defending Christianity. The mystery cults were the main focus of the attack. This brings some questions to the modern researcher: how did Firmicus reconcile astrology with Christianity? Did he consider them mutually exclusive?

Interestingly, there is no mention of astrology in The Error of the Pagan Religions. It is possible that Firmicus did not consider that his attack included astrology but only other aspects of Paganism. Another hypothesis is that he converted after the writing of the Mathesis, if it preceded The Error. In any case, both are very informative of the situation of the Roman Empire in the mid-fourth century A.D., including its view on the importance of astrology, the Christianization of the Empire, and all the controversy that it caused.


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