Episode 27: Astronomica

March 10, 2023

In this episode we examine the work of two Roman astrologers to see how Roman astrology worked in practice: Marcus Manilius, who wrote Astronomica, and Firmicus Maternus, who wrote the Matheseos.


Good evening, and welcome to the Song of Urania, a podcast about the history of astronomy from antiquity to the present with new episodes every full moon. My name is Joe Antognini.

Last month we got a taste of the rather extensive political dimensions of astrology in ancient Rome. But the episode was focused mostly on why astrology was so influential in Rome and how the state tried to regulate this influence. But I had little to say on what the astrology of ancient Rome actually consisted of. In this month’s episode I’m going to try to remedy that by talking about one of the earlier and more complete descriptions of Roman astrology that comes to us through a work by a first century astrologer named Marcus Manilius entitled Astronomica.

Now, I normally like to start these kinds of discussions by putting the person first and saying a little bit about their life. But in this case it’s very hard to do because as with so many figures from the ancient world we know basically nothing about Manilius’s life. The only thing that survives of him is just this work. No other Roman author even so much as mentions him. The only way we can even date the work is thanks to a couple of references to contemporary events that Manilius makes in the Astronomica. The most important one is a reference to the Battle of Teutoberg Forest of 9 AD. This was a catastrophic defeat for the Roman Army in which three full legions were ambushed and slaughtered by a coalition of Germanic tribes, and it’s hard to overstate the effect of this defeat on the Roman psyche. It was not only an enormous loss in terms of the sheer number of soldiers lost, but to the proud Romans it was a humiliating defeat as well, and it shattered the Roman’s sense of invincibility and set the northern bound of the Roman empire at the Rhine. At any rate, some small sense of the impact of this event in Rome can be seen by the mere fact that it’s referenced in a work on astrology. But for our purposes the main importance of Manilius mentioning the Battle of Teutoberg is that we can be sure that the work must have been written sometime after 9 AD.

The second reference in the work that helps us to date it is a reference to the emperor. Unfortunately the emperor is simply referred to as “Caesar,” which is what all emperors were called in Rome, and so on its own isn’t especially helpful. But from the surrounding context it is probably referring to Augustus. Since Augustus died in 16 AD, the work is usually dated to sometime in the second decade of the first century. But it’s also possible that Manilius wrote the text after Augustus had died and was simply referring to the deceased emperor, or possibly that he was referring to his successor Tiberius.

So that is really all we can say with some certainty about Manilius’s biography. There is even some dispute as to whether or not Manilius was actually Roman at all. Historians have periodically suggested that he was perhaps an educated Greek slave. The main motivation for this theory is that over the centuries literary critics have generally derided the quality of Manilius’s poetry, and this led to the supposition that perhaps his poetry was so bad because Latin was not his native tongue. And furthermore, despite my earlier assertion that no other Roman authors mention Manilius, there is in fact one passing reference by Pliny the Elder to an individual that might have been Manilius. Pliny was writing a kind of encyclopedia called the Natural History in the mid first century AD, and in this work he was talking about chalk, and in particular he went into the details about the kind of chalk that was used to color the feet of slaves when they went up for sale. In this discussion he mentions one such slave, named “Mannilius Antiochus” who he says is an astrological writer. But Pliny states that this individual was active in the mid first century BC, which is far too early since we know from the reference to the Battle of Teutoberg Forest that Manilius must have been writing after 9 AD. It’s possible that Pliny was just way off on when he thought Manilius was kicking around, but given that the Astronomica had only been written about 40 or 50 years earlier, it seems like a big mistake to make. It would be like someone today talking about how Steven Hawking was thinking about black holes in the 1890s. So the most probable interpretation is that there were just two astrologers over the years in Rome who both happened to have the name “Manilius.”

So, there’s not much hard evidence to support the idea that Manilius was in fact a Greek slave. And on the other side, there are a few aspects of his writing which seem to support the idea that he was a native-born Roman. While it’s true that Manilius had his fair share of critics, there have also been defenders of his poetic style. His Latin might be a little inelegant, sure, but it’s oftentimes complex, which you might not necessarily expect of a non-native speaker. And more importantly, the overall viewpoint he presents in the text is very Roman-centric. He talks of himself as being the first to write about this “foreign” subject of astrology, which seems to imply that he is the first Roman to do so. He refers to Latin as “our” language, calls Rome, “the greatest of all things,” and generally shows a lot of rah-rah Roman pride. He identifies the constellation Libra as the symbol of Rome because it represents justice and empire. And when he talks about the Milky Way he says that the multitude of stars it contains are the souls of great men who have ascended to the heavens. He acknowledges that, yes, of course there are men of all nationalities up there, but most of them are Romans.

Now, as I mentioned earlier, other than that one dubious reference by Pliny, Manilius’s name appears nowhere in the ancient literature. The Astronomica just stands alone as a completely independent work. So, for this reason, it’s hard to say whether or not the Astronomica is the best exemplar of first century Roman astrology. At least from what we have, it seems as though this work had no impact whatsoever and was totally ignored by the author’s contemporaries and all the rest of the Romans down the ages. Now, it’s possible that this is not true — perhaps many people read it and just never felt the need to cite it explicitly. Or maybe some people did, but their works were lost. As with so many things in the ancient world it is hard to say. But at least as a point of comparison we can look back to the poem Phaenomena of Aratus that I mentioned back in Episode 16. We know that this work was enormously popular because it was widely referenced throughout the Hellenistic and Roman world, and some of these references state that it was actually used as an astronomy textbook for schoolchildren. But nothing of the sort exists for the Astronomica of Marcus Manilius, so it’s very hard to say how well received this work was, except that we can be pretty sure it wasn’t a blockbuster in the same way that Aratus’s Phaenomena was.

Because it seems to have been a fairly obscure work, its textual history is a bit interesting. It seems to have survived in various monasteries over the centuries and went unnoticed until 1417, when an Italian scholar named Poggio Bracciolini found it in some library or other, either in France, Germany, or Switzerland, he didn’t say. Bracciolini couldn’t take the original back home to Italy with him of course, that was out of the question, so he hired a scribe to make a copy of the document. But he seems to have done a poor job choosing his scribe because the copy his scribe made was terrible, riddled with errors, and he complained that his scribe was “ignornantissimus omnium viventium,” the most ignorant of all the living. Well, even after its discovery in the 15th century, the text was still basically ignored until the early 20th century when the great classicist A.E. Housman devoted much of his scholarly life to translating and annotating the text. Housman’s decision to expend so much effort on this one text bewildered his fellow scholars, and the bewilderment continues right down to this day. In his time, Housman was considered to be one of the most knowledgeable classicists of all time, a true giant in the field. Now, the Astronomica is an okay work and all, but let’s face it, Greek and Roman literature have a lot more to offer. So seeing this great figure spend so much of his life on such a middling work has long been a disappointment to classicists. To make a perhaps unfair analogy it would be a little as though the young Jimi Hendrix, rather than picking up the guitar, decided to spend his life learning to play the kazoo. I’m sure he would have been a great kazoo player, but the rest of the world would have wondered what could have been if he had chosen an instrument worthier of his talent.

Okay, so that’s the little we know about the man who wrote the text and how we came to be aware of it. So let’s turn now to the text itself. One thing to mention right off the bat is the title of the work, “Astronomica.” In modern terms the text is about astrology, but in the ancient world, there was no real distinction between the terms astrology and astronomy. The ancient Greeks and Romans did recognize a distinction in the subject matter between what we today call astronomy and astrology — Ptolemy, for example devoted his Almagest to astronomy and put his astrological material in the Tetrabiblos. But there weren’t separate terms used to label these two subjects. Ancient authors used the terms astronomia and astrologia more or less interchangeably to refer to the generic study of the stars. If one were to force a distinction, astrologia was perhaps the more general term whereas astronomia was associated more with Plato and his school and could be more esoteric. So, although from a modern perspective a book entitled Astronomica would purport to be about astronomy, it was a largely astrological work.

Manilius divided the Astronomica into five books. At a high level, the first book presents a description of the universe, and especially describes the constellations. The second and third books focus on the zodiac, the band of constellations along the ecliptic, the path of the Sun in the sky. These first three books form the astronomical foundation. The fourth book then dives into the real meat of the astrology and describes the influence of the zodiac on Earth. The fifth book then presents some cutting edge astrological research and talks about the influence of constellations that are not in the zodiac on the Earth.

Astronomica shares a common feature of other treatises on astrology from the era and opens with a defense of the value of the study of astrology. Manilius opens by saying:

By song I undertake to draw down from heaven the divine arts and the stars, knowledgeable of fate, which govern the diverse fortunes of men, a work of divine reason.

Now as I mentioned earlier, while the ancient Greeks and Romans didn’t use different terms to distinguish astronomy and astrology, they recognized that the two were distinct subjects, and Manilius argues that astronomy is a beautiful subject, but nevertheless it is only the foundation of a much more beautiful subject, namely astrology, to use the modern terms. Of astronomy he says:

It is pleasing to walk through the air itself and live strolling in the immense sky and to learn about the constellations and the contrary movements of the planets.

But then goes on to say:

It is more pleasing to know in depth the very heart of the universe and to see how it governs and brings forth living beings by means of its signs and to speak of it in verse, with Phoebus providing the tune.

In other words, astronomy is wonderful and all, but in the end astrology is the higher subject. Nevertheless, Manilius cautions the reader that it is necessary to learn the foundations of astronomy before proceeding to astrology:

And since the song descends from high heaven and the fixed order of fate comes to Earth, I first must sing of the shape of nature and fashion the image of the entire universe.

And so he spends the first book doing just that. Now, nothing in his overview of the fundamentals of astronomy will be especially novel to us now that we are intimately familiar with ancient Greek astronomy, but it is a good summary of what we might call the standard model of the universe in ancient Greece and Rome that educated people all more or less had in their heads. The model is basically the same one that Aristotle had proposed three centuries earlier with a few modifications. The universe consists of two spheres: a hollow outer sphere made of fire, which constituted the heavens, and an solid inner sphere made of Earth which constituted, you guessed it, the Earth. Manilius even rehearses the usual arguments for the roundness of the Earth. He makes the philosophical argument that the sphere is the most divine shape, and therefore most worthy of the universe. And he answers the objection about why the Earth does not fall down by reviving Anaximander’s argument from five centuries earlier that the Earth does not fall due to symmetry — it is equidistant from all other points in the universe so it cannot chose a direction to move. Then he goes on to the empirical arguments with varying degrees of success. He makes the point that if the Earth were flat, we would be able to see all the constellations at once, but some constellations are only visible in summer, and others are only visible in winter. So far so good. Then he brings up lunar eclipses as another argument for the Earth being round, but unfortunately here he mangles the argument. Manilius says that we can tell that the Earth is round because lunar eclipses are not visible everywhere on Earth. But in fact, lunar eclipses are visible everywhere on Earth, at least everywhere that it is night, and either way this doesn’t really have any bearing on whether or not the Earth is round. The real argument is that the shadow the Earth casts on the moon is always curved no matter where on the sky the eclipse occurs. But Manilius seems to have not understood this argument. As an aside, Manilius also makes a number of other rather basic errors about astronomy in the work which has led to some speculation that he may not have primarily been an astrologer but was first and foremost a poet who happened to be somewhat learned on matters of astrology, somewhat like Aratus.

Now Manilius does not give any indication as to the size of the universe, but he does point out that the distance from the Earth to the heavens is equal to the length of two signs of the zodiac. Since each sign is 30 degrees across, this means that he has effectively set pi to be exactly 3. A.E. Housman commented with sarcasm that “the brightest facet of Manilius’s genius is his eminent aptitude for doing sums in verse.”

Now one of the interesting bits of his overall description of the universe is how he treats the creation of the universe. The earlier philosophers of the Ionian school had some theories about how the universe came to be, and Plato said a great deal about it in the Timaeus. But the Greeks didn’t really have a consensus view on the creation of the universe. If we look at their myths, the creation myth is fairly vague relative to other cultures — certainly compared to the creation story of the ancient Israelites to the east. In Hesiod’s telling, there is this idea that in the beginning was a primordial god called Chaos. Then Gaea the Earth, Tartarus the Underworld, and Eros, Love, came into being. But it’s not really clear whether or not these deities spring from Chaos directly or just came into being independently. At any rate, the myth more or less just lists which gods or goddesses sprang from which others and the stories don’t really get going until you get to the Titanomachy, when the Olympians rebelled against their elders, the Titans. With the exception of this brief story from Hesiod about Chaos, the Greek myths essentially take the existence of the universe for granted. So Manilius looks at the paucity of thought on the subject and the diversity of those few theories that do exist and concludes that we really don’t know anything about the topic. Today we might commend him for his intellectual modesty. He says:

The origin of the universe will always be a matter of controversy, and doubtful will remain that which is hidden and is so far beyond man and god.

This is particularly interesting because to Manilius, the creation of the universe is not only beyond human understanding, but is beyond the understanding of the gods as well. Whoever created it, though, was evidently an extraordinary artist. As an another aside here, the Roman author Varro argued that the Latin word for heaven, “caelum” was derived from “caelatum,” which meant “engraving” as though the creator of the universe had engraved the stars by hand onto the sky. Nevertheless, however it got here, Manilius falls over himself to praise at length the rationality and elegance of its structure.

And here, I think it’s worth pausing a moment and trying to get inside the mindset of those in the ancient world. In the modern world, we’re very familiar with clockwork machines and we have all grown up at least implicitly with a highly mechanistic worldview. Whether or not we have learned much physics, we learn, at least through osmosis in the culture a picture of the universe that is deterministic. The laws of physics rule all and mechanistically drive all matter in the universe forward in time. But the ancients had no such conception. Their world was a world of patterns, but not absolutely repeating patterns. They could note the pattern of winter followed by spring and spring followed by summer, but each summer differed somewhat from the summer that came before and the summer that came afterwards. Everyone had the same phases of life from childhood to old age, but no child was identical to another. But the heavens were the one exception in all this, and this was of considerable note to the ancients. Everything on Earth changes — no pattern repeats itself precisely. But in the heavens, the same stars rise every night in precisely the same configurations. The same stars are visible in summertime year after year after year. They knew of nothing else in their life that had the same precise regularity. Now, the modern view is to take this regularity as the default — if things are behaving randomly, the impulse is to investigate and see what is causing two things to be different. This is, in a nutshell, the whole scientific method. You take a system and hold everything you can constant while you try to change just one parameter to see how that affects its behavior. But to the ancients, variation was the norm. Regularity was the exception. And it was a mystery. Manilius writes:

But why do we observe the constellations rise in an appointed rhythm and run their prescribed course as if by command, without any racing ahead or being left behind? Why do always the same stars adorn the summer nights and the same the winter nights, and why does each day impart to the sky a specific appearance at both its arrival and its departure?

Manilius proclaims how remarkable it is that the description of the skies in Homer centuries in the past matches the sky he observes today.

All things created according to mortal law are changing and with the years turning, the lands do not know that they take off and put on new appearances through the ages. But heaven remains unchanged and preserves all its characteristics; long time does not increase it and age not diminish it, and its movement affects it in no way, nor does its course wear it out. It will always be the same because it always was the same. Our fathers saw it no different, nor will our grandsons.

Manilius then starts to describe the various constellations of the sky. Since his main aim is astrological he starts with the zodiac, beginning with Aries at the vernal equinox. Then after finishing up with the zodiac he describes the circumpolar constellations and in particular notes how Greek sailors use the Great Bear to navigate whereas Phoenicians use the Little Bear. Then he describes the rest of the northern constellations followed by the southern constellations that are visible from Rome. But Manilius recognizes that this does not cover the whole celestial sphere — there are regions of the sky which he is too far north to see, so he speculates about what some of these unseen stars very far south might look like. His sense of symmetry and intuition that the universe has been rationally constructed leads him to the conclusion that probably there is a Great Bear and a Little Bear around the southern celestial pole just as there are around the northern celestial pole, along with a southern analog of Draco.

As he’s going through all these constellations, much like Aratus did earlier in his Phaenomena, Manilius entertains his reader by regaling them with all the mythical stories associated with each of the constellations. But in the end, Manilius advises his readers not to put too much stock in the truth of such stories and to beware so-called astronomers who have nothing to tell you about the sky but amusing stories.

Now, one feature of the constellations that annoys many of us today is that the constellations purport to be various things, a ram, a bull, a hunter, a dog, and so forth, but when you look at them, they don’t really look like anything of the sort. How can you tell that that’s what they’re supposed to be? Well Manilius answers this question for you. In his telling, they necessarily have to be mere outlines of the figures they are meant to represent, because if they were filled in with stars, there would be so many stars that the whole sky would ignite. But if you’re having difficulty recognizing the shapes, Manilius recommends that you look at the constellations when the Moon is full since it will wash out the fainter stars and make the bright stars stand out more. Having been in a very dark site myself, this is good advice for the ancient world, but it unfortunately won’t work for most of us today because the main problem we now have is that the sky is so bright in populated places that many of the constellations cannot be seen at all.

Well, after laying out the constellations arrayed across the heavens he then spends quite a bit of time describing the various astronomical circles, the celestial equator, the tropics, the zodiac, and so forth, along with the Milky Way, and once Manilius has laid the astronomical foundations he’s ready to dive into astrology proper. Now I’ve already said a fair amount about the different categories of astrology in previous episodes. In the last episode I talked about the tension between fatalistic and catarchic astrology, fatalistic astrology being the more extreme interpretation of the two in which the omens written in the stars are unalterable. Catarchic astrology, by contrast, only claims that the stars have a general influence on the Earth, but this influence can be overcome. For his part, Manilius comes down squarely on the side of fatalistic astrology. The most famous line from the book is the Latin motto “fata regunt orbem, certa stant omnia lege,” which translates to “fate rules the universe — on immutable law, everything rests.” One thing I should have mentioned in the last episode, however, is that the term catarchic astrology has a dual meaning, it can also be the use of astrology to make predictions about when is the optimal time to do something. But this term was generalized to mean the general attitude that the predictions of the stars were not absolute since the only reason you would determine the optimal time to do something is to change your own behavior, which would be impossible if everything was completely predetermined. Besides catarchic predictions, the other main use case of astrology was what is called either natal astrology or genethiliacal astrology if you aren’t into the whole brevity thing, and this is the practice of reading the horoscope of an individual’s birth to determine the main features of their life.

Aside from the fatalistic-catarchic distinction, another big fault line in astrology that I have discussed was what is called mundane vs. individual astrology. Mundane astrology has to do with reading the heavens to determine great things, the fates of kings and nations, the coming of wars and plagues, and so forth, and calling this mundane might sound like something of an oxymoron but it derives from the Latin “mundus” meaning “world”. By contrast individual astrology is, as you would expect, all about predicting the events of an individual’s life. Of the two Manilius is only really interested in individual astrology. He has about 250 lines devoted to astrological geography in which he argues that the animosities and alliances among the zodiacal signs are paralleled on Earth by the animosities and alliances among the people down below. But even that is laid out for the purpose of reading an individual’s horoscope since the location of a person’s birth will influence the reading of the stars.

But there was another general aspect of ancient astrology that I have not mentioned, and this was a theory of how astrology actually worked. The whole idea of the field is to observe the heavens and use these observations to make predictions about life here on Earth. Now we, today, at least those of us of a scientific bent, find astrology a little absurd because the stars are so far away — how can they possibly have any influence on us? We envision the direction of causality as going from the stars to us. But this was not Manilius’s view. To him, and, really, to many ancient astrologers, the heavens did not directly cause anything on Earth — instead they were simply signs of what happened on Earth. To put it in more formal modern language, if we see that thing A is correlated with thing B, there are three possibilities. In the simplest cases we could have that A causes B or B causes A. But there is a third possibility, that there is some other thing C which causes both A and B. So we could have that the heavens cause things to happen on the Earth, or we could have that things on Earth cause things to happen in the heavens, though that possibility was universally rejected, but it could be that there is some other thing that causes both things to happen on Earth and things to happen in the heavens. This was the position of Manilius. Now, what this other thing was was always a little vague. He more or less chalked it up to divine providence and a belief in a general “sympathy” that pervaded the universe and caused all things to move in harmony with each other. Now this theory was not universally accepted. Ptolemy for his part a few centuries later took the more materialistic position and supposed that the stars directly caused events here on Earth.

Manilius’s picture of life on Earth paralleling the heavens can be seen in his discussion of stellar brightnesses. He notes that the stars are of all different brightnesses, and there are more and more stars at fainter and fainter magnitudes. In his telling, the faintest stars are as numerous as the grains of sand on the Earth or the leaves falling in the forest, and he analogizes this distribution to human society. Just as there are a multitude of faint stars, then a smaller number of stars of moderate magnitude, and only a handful of very bright stars, so it is in our society. There is the vast unwashed mass of those without citizenship, then there is the smaller number of common citizens, then you have yet fewer equestrians, and finally, there are are only very few senators. Reading between the lines here, Manilius makes an interesting omission. He ends his hierarchy with the senators — but he was writing this toward the end of Augustus’s rule — so where is the emperor? Scholars have wondered whether Manilius was perhaps making a subtle republican point here. But it is a little hard to read too much into it because in the early empire, Rome operated under the fiction that the emperor was simply the first among equals.

At any rate, as part of his defense of astrology Manilius presents a kind of history of the subject. The most important thing Manilius wants you to know about it is that it is very ancient and ultimately came from the god Mercury. From Mercury, it was revealed by the gods to kings. And as an aside here, this was very much in line with the ancient worldview. Kings were the closest to the gods, just a hair below them. And in many cases kings were in fact promoted to divinity. So this view that the knowledge of astrology came to man from the gods through kings made perfect sense. From the kings it was passed on to the priests who then had been practicing the art since time immemorial. Critically, they had been doing this for so long that an entire Great Year had passed, a Great Year being the time it takes the Sun, Moon, and all the planets to return to their initial configurations. What exactly the length of the Great Year was varied from astronomer to astronomer, some pegged it at a few thousand years others went as high as a few million. But either way, the important thing was that astrologers had been observing the sky that entire time, so that today, no sky is unique. It had been observed before and earlier astrologers had seen the consequences on Earth. This was why you could have absolute faith in the practice of astrology. It may be a difficult subject to do properly, but it was tried and tested and there was nothing new under the Sun.

Okay, so with that all out of the way, Manilius starts to get into some of the mechanics of his astrology. If you were to read a horoscope, what you would do is draw a large circle which is the stage on which everything happens and represents the position of the zodiac on the sky at the time of an individual’s birth. On the left hand side of the circle is a point called the ascendant, which represented the eastern horizon, so this would tell you what sign was rising at the time of someone’s birth. This was generally the most important point and drove the entire astrological analysis. In Greek the term for this point was “horoscopus,” which is how we get the more general term “horoscope”. At the top of the circle you have a point called midheaven which represents the point on the zodiac that is highest on the sky. Then to the right you have the descendent, which tells you which sign is setting, and finally at the bottom of the circle is a point called lower midheaven, which is opposite the highest point of the zodiac and is under your feet, and so is not visible. Collectively, these four points are called the “cardines.”

There are then three ways to analyze an individual’s horoscope. First, you can look at what signs the various planets are in. Then second, you can look at where the signs of the zodiac are relative to the cardines. And, in fact, Manilius divides it up further, each quarter of the circle gets divided into three slices so that there are twelve divisions to the circle in all, called “places” or “houses.” Now one subtlety here is that this was an equal division of the circle in the diagram, but it wasn’t actually an equal division on the sky. Because the zodiac is inclined on the sky, the angles subtended by each of the houses varied over the course of the year. During winter when the zodiac is high on the sky, the width of the houses above the horizon was larger, and in summer when the zodiac is low it was smaller.

This division was known as the dodecatropos, and each one corresponded to a different aspect of a person’s life: health, marriage, children, parents, death and so forth. So you had these two configurations that the astrologer had to keep track of: which planets were in which signs, and which signs were in which houses. But there was a third configuration, too, and this was what was called the system of Lots. Now the system of lots appears in other astrological expositions, but Manilius’s method is unique. Like the system of houses, the system of lots divides the circle of the zodiac into twelve equal slices. But now, rather than setting them based on the horizon, they are variable and are set based on the position of the Sun and Moon. The procedure Manilius says is that if the individual was born during the day, find the angle from the Sun to the Moon, moving counter-clockwise. Then, starting at the ascendant, go that number of degrees above the ascendant. But if it is night, however, you use the angle from the Moon to the Sun rather than Sun to the Moon. This sets the position of the first lot. Then the rest of the lots increment counter-clockwise around the zodiac. As with the houses, each lot corresponds to some aspect of life. In Manilius’s system, for example, the first lot tells you about wealth, the second about warfare and travel, the fifth about marriage and friendship, the eleventh about health, and so on.

These three sets of configurations produced a huge combination of possibilities that the astrologer could analyze. But in order to do this, of course, one needs to know what the sky looked like at the time of a person’s birth. Now, the simplest method is to assume that a new sign rises every two hours. Based on the day of the year and the time of the birth, you could then fairly easily figure out which sign was where. This is the so-called “common method,” but Manilius advises you not to use it. The problem is that the signs do not rise exactly every two hours. Because the zodiac is inclined on the sky, some of the signs rise more quickly and others more slowly. But figuring out how to do this correctly is quite complicated, so Manilius conveniently provides an alternative method: just assume that half a sign rises every hour. Now if you think about it, this is exactly the same as assuming that a whole sign rises every two hours which Manilius just told you not to do. Housman, in his usual acerbic style, says:

Alas, alas! This alternative method of yours, my poor Marcus, is none other than the vulgar method which … you said you knew, and which … you exposed as false. The wolf, to whom in his proper shape you denied admittance, has come back disguised as your mother the goose, and her gosling has opened the door to him.

To understand the significance of each sign in a particular house or lot, Manilius describes the qualities of the various signs of the zodiac. Once again, there is a huge number of attributes that each sign carries. Signs can be masculine or feminine, animal or human, fertile or infertile, terrestrial or aquatic. Mostly you could guess these attributes, but not all. Taurus the Bull, for instance is considered a feminine sign. Virgo is considered to be infertile. Some are single, others double. If you look at the constellations, Taurus, Gemini, and Cancer they all appear to be looking backward from the direction they travel on the heavens, and this is naturally significant as well. These attributes then produce relationships between them. The animal signs and human signs are generally opposed to one another. Some of the masculine signs are in love with various feminine signs, but sadly this celestial romance is unrequited.

In Manilius’s telling, the zodiac is a loud, quarrelsome place, with the various signs antagonizing each other. The strongest enmities are between signs on opposite sides of the zodiac to each other. These signs could never share the same sky — as one rose another would set, as though they could not even stand the sight of each other.

But there were sympathies between some of the signs as well. The strongest of these is the trigon, or a set of three signs that form an equilateral triangle. Manilius claims that the trigon has the greatest influence because the path connecting the signs comes the closest to Earth. Next is the quartile, which are the signs that form a square together, and finally, sextiles, which are signs that form a hexagon together and which have the weakest influence.

Each of the signs has their own professional associations. For example, Leo, being a lion, is most relevant to hunters and butchers. Aries is most relevant to wool workers. Taurus to farmers. Pisces is most relevant to fishers, sailors, and shipbuilders, and Scorpio is associated with soldiers and gladiators. Gemini gets associated with poets and astrologers, which might seem a little out of left field, but one of the interpretations of Gemini was that the twins represented Apollo and Mercury, the gods of poetry and astrology respectively.

Manilius then divides each sign into three sections 10 degrees wide, called dodecani. I mentioned these in the last episode and they seem to have been due to Egyptian influence since the Egyptians had 36 zodiacal signs rather than the 12 of Babylonian and Greek astronomy. Each sign was also divided into 12 segments of 2.5 degrees called dodecatemoria. Each one of these 12 dodecatemoria in a sign was in turn associated with its own subsign. Some of these were “partes damnande” in Manilius’s terminology and would negate or impair the usual effect of the overall sign. Since there are 144 dodecatemoria in all, this part of the poem where Manilius explains which ones are good and which ones are bad is a bit monotonous. Finally, each dodecatemorius is divided into five half degree segments, each of which is, in turn, associated with a planet. Needless to say, this is a complicated system and Manilius admits that he can only give a cursory treatment. But, never fear, he says he will give a complete exposition in the future. But, if he ever did, it’s not in the Astronomica.

There are other details that the astrologer must consider as well: a lunar eclipse would have the effect of cancelling out the sign that the eclipse occurred in. And this was not limited to the duration of the eclipse, the effect would persist for about a year, and then would pass on to the two preceding signs which would then weaken. Finally, in his last book Manilius delves into the cutting edge astrological research of the day, the effect of the so-called paranatellonta. These were the constellations outside of the zodiac. Ordinary astrology was exclusively concerned with the constellations of the zodiac. The rest of the sky might as well not exist. But the thought was that there might be some additional astrological signal by considering which non-zodiacal constellations were rising at the time of an individual’s birth. Here Manilius gives quite a complete tour through much of the sky and enumerates the associations of 33 constellations. Canis minor, for instance, the little dog, is associated with dog breeders, Argo, the ship, is associated with sailors, Auriga the Charioteer, is associated with, charioteers. Ophiuchus the snake handler is associated with, you guessed it, snake handlers. And Manilius doesn’t just rattle these associations off, he describes each of these professions in quite some detail, so this section is actually quite a charming window into everyday life in ancient Rome. Manilius’s discussion of Cetus the whale, for instance, includes 14 lines on the subject of the various ways that fish sauce can be made.

Well that is pretty much it in the Astronomica. Now let’s say you decide to go and use what you have learned from this work to cast a few horoscopes yourself. You’ll immediately hit a difficulty. Manilius describes all the aspects of the zodiac in thorough detail — but how do you know which signs are relevant when? You’re supposed to look at which planets are in which signs. But what do the different planets mean? Thinking back, I never really talked about the planets at all. In the entire Astronomica, Manilius devotes just about four lines to describing the planets. But of course the interaction of the planets with the zodiac is the most important part of the whole thing! This has always been the most baffling feature of the Astronomica. Katharina Volk described the astrology Manilius tells you in the Astronomica as “like a gameboard without pieces, a football field without players or a ball.” To take the analogy a bit further, if you’re familiar with the board game the Settlers of Catan, it’s rather as though Manilius told you all about the various kinds of hexagonal tiles, the wheat, the ore, the clay, the desert and so forth, but then never told you anything at all about the game pieces, the villages, the roads, and the cities. You’d know a fair amount the board game, but you certainly wouldn’t be able to play. And as an aside here, this analogy to a game board really isn’t so far off because the way that ancient astrologers would often conduct their sessions was with the aid of a large board that would represent the zodiac. Then the astrologer would place gemstones at various points on the board to represent the positions of the planets to explain different aspects of the horoscope. But the entire Astronomica is essentially devoted to just describing the board itself and says nothing about the placement of the gems.

So why is there this glaring omission? There are a couple of possibilities. One is that he did in fact include it, but that part of the work got lost. The main difficulty with this explanation is that it’s hard to point to where in the text a section went missing. There are a few places where there seems to be some missing text because a line gets cut off or the text suddenly jumps from one subject to another. But if Manilius did give a decent treatment of the planets, it would have to have been very long because that was really at the core of astrological theory, and nowhere in the text do these gaps between subjects seem large enough to accommodate a topic like that. Another option is that maybe it came at the end as a sixth book which got lost, or that the Manilius intended to put his discussion of the planets at the end, but just never got around to it and left the work unfinished. But the book has a fairly logical progression and the conclusion seems polished so it doesn’t seem as though the book suddenly ended halfway through. Another alternative is that, despite his promises at the beginning of the work, Manilius may not have wanted to give too much detail about how astrology actually worked in practice, certainly not enough for the reader to actually go out and cast their own horoscopes. After all, he was writing this work in the second decade AD, and you’ll recall from last episode that this would have been after Augustus’s edict of 11 AD which put severe restrictions on the practice of astrology. Given the risky subject matter he was dealing with, he may have decided to withhold the more sensitive technical details about how to use the planets to interpret a horoscope and presented only the more poetic descriptions of the various features of the zodiac and celestial sphere. Or, perhaps he was first and foremost a poet rather than an astrologer and found the descriptions of the zodiacal constellations more amenable to verse than the motions of the planets.

Well, before we forever abandon the wasteland that is Roman astronomy, I would be remiss if I did not mention one last Roman astrologer, a man by the name of Firmicus Maternus. Firmicus was a Roman senator from Sicily who was active in the first half of the 4th century AD. He pursued law when he came of age and spent the early part of his career battling organized criminal networks in Sicily. Evidently the Sicilian Mafia was just as much a problem in late antiquity as it is today. In midlife he was promoted to the rank of senator and befriended Lollianus Mavortius who was a consul and former governor, and it seems that the two connected over a mutual interest in astrology. Firmicus must have been the more learned of the two on the subject and decided to write an exposition of astrology for his friend. The resulting text, called the Matheseos, is the longest surviving astrological text in Latin. Later in life Firmicus wrote a second text, called “On the Error of Profane Religions,” which was a defense of Christianity, a religion that was fast becoming popular among upper class Romans after Constantine began to publicly embrace it earlier in the century. Firmicus probably converted to Christianity later in life, after having written the Matheseos, but we cannot say with certainty, which is unfortunate because otherwise Firmicus would have been a very interesting data point on the relationship between early Christianity and astrology. If he was a lifelong Christian, presumably he believed that astrology was compatible with Christianity. But if he converted later in life, as is more probable, did he reject the astrology he had practiced in his youth? Sadly we don’t know.

Either way, the astrology presented in the Matheseos is highly influenced by Stoicism and Firmicus is firmly in the camp of fatalistic astrology. To him, only fatalistic astrology could explain the otherwise inexplicable twists and turns that we see in our own and others’ lives. He writes:

Consider the youth at the height of his physical development – rich, innocent, modest. Driven by no private crime, by no anxiety, he has hanged himself… Another man, known to everyone as innocent, fell on a drawn sword… A just man maintains his life as a wretched beggar while another, stained by well known crimes, accumulates the highest honours… To what do we attribute all this?…. Give us your hand for a little while and hold back from arguments. Soon you may agree that all that stumbling and weak mortality must bear are decided by the chance movements of the planets.

The eight books of the Matheseos follow a structure that should by now be fairly familiar to us connoisseurs of ancient astrology. The first book presents a defense of the practice and tells you just how powerful it is and how much you can read of a person’s life, if only you take sufficient care to practice it correctly. Then Firmicus goes over the fundamentals of astronomy, the creation of the world, and then he gets to the good stuff that Manilius left out, how to interpret the planets. The fourth book is devoted to the specific topic of how to interpret the position of the Moon. The fifth book is largely missing, but by book 6 he has moved on to more advanced topics like how to interpret combinations of planets like conjunctions, oppositions, trines, quartiles, and so forth.

For the casual reader the most interesting book is Book 7, which starts to make specific relations of the configurations of the planets to various circumstances on Earth. This, then, is what ties everything together and places in the reader’s hands the power to read the heavens. But before granting the reader such power, he impresses upon the reader that they must use this power responsibly and beseeches the astrologer to take an oath to only use this power for good, much as the ancient physician Hippocrates urged his students to recite his own oath. Firmicus’s oath goes as follows:

We beg you to take an oath that these revered doctrines will not be revealed to profane ears but that the entire teaching of divinity will be made known only to those equipped with pure splendor of mind, whom an uncorrupted soul has led to the right path of life, whose loyalty is above reproach, whose hands are free of all crime. Receive, therefore, the detailed account which with the greatest trepidation of spirit we have promised you.

I’ll pause for a moment now so that you can swear the oath and then we can proceed.

Okay, now that we have agreed to use this knowledge for good, what kinds of things can we predict with Firmicus’s astrology? Now, in the interest of time I can’t go into through each and every category Firmicus presents as there are twenty-six of them. But they range from the mundane to the terrifying. On the more mundane end he has a formula to predict whether or not an individual will go bald:

When the Moon is on the angles and in signs which are without hair or in Sagittarius, and the malefic planets are in fixed or tropical signs in the house of illnesses and afflictions, the native will be bald. The same is the result of Venus in her own house on the midheaven. But Saturn between the Sun and Moon will make them gray at an early age.

Firmicus covers numerous illnesses and maladies as well, whether or not an individual will go blind, suffer from epilepsy, insanity, paralysis, or a difficult childbirth. For example:

If the Sun and Moon are both located on one angle, or on different angles, and are in opposition or square aspect, if malefic planets hold both anaforas, that is, of the Sun and Moon, this indicates blindness of both eyes.

Some of the sections of the seventh book implicitly rebut a number of the arguments that had been leveled at astrology by its skeptics. You’ll recall that one of the critiques was that there was no reason that it shouldn’t also apply to animals. And Firmicus says indeed, why not and has a section on predicting the fates of animals. For example:

If Mars is in opposition or square aspect to the Sun or Moon on the ascendant, the quadruped which was born will be destined for public sacrifice.

The other main critique was that astrology didn’t have a good explanation for the different fates of twins. Now, Firmicus doesn’t address this conundrum head on, but he does at least give you some tools to anticipate the problem by predicting whether or not a pregnancy will result in twins.

In addition to these more prosaic kinds of predictions he has a variety of more salacious formulae. Will someone become a homosexual or a prostitute? Here you must be careful because different configurations have different implications for men and women. A particular configuration may be benign for a women but will cause a man to inevitably sink into a life of prostitution. However, a worried parent may at least find a silver lining in that some signs point to the individual becoming no ordinary prostitute, but one of high station. But that’s not all, Firmicus tells you how to determine if someone will be castrated, or publicly engage in sexual perversion, or commit incest.

Many of Firmicus’s formulae are darker. There is quite a long section on infanticide. Infanticide was a tragically common practice in ancient Greece and Rome. As a general rule infants with any visible deformities would be abandoned, but any infant could be abandoned for any reason. A newborn child would be presented before the family patriarch who had the right to decide whether to keep the child or not. Now, the Greeks and Romans didn’t think of themselves as savages — they thought that murdering the infant directly was too cruel. Instead the preferred method of infanticide was through exposure — they would simply abandon the child somewhere out in the wilderness. They could then rationalize that they had not killed the child themselves. Indeed, if the gods willed the child to live, a passerby would come upon him or her and take the child in — or they might even be raised by animals as in the myth of Remus and Romulus. Since the child had been left alive, this naturally led many grieving mothers to wonder what had become of their child and to consult astrologers to find out. Based on Firmicus’s formulae, the prognosis was generally not good. Most of the time Firmicus predicts that the infant will die, oftentimes eaten by dogs, or sometimes drowned. In one case the infant will be taken in by a stranger but will nevertheless perish a few days later.

Another gruesome section deals with violent deaths and explains how certain configurations of the planets indicate that an individual will see a violent end and that the particular signs these configurations occur in determine the manner of the death. If the configuration occurs in a watery sign, for instance, the hapless individual will die by drowning. An Earth sign portends a natural disaster. If Mars is involved one will die in war or some sort of fight. There are methods to predict death by hanging, hemorrhage, or being devoured by beasts.

All this is certainly part and parcel of ancient astrology. To broaden the discussion, one of the general features you find in ancient astrological texts is that the predictions tended to have a kind of binary quality. If you went to an astrologer, you’d be unlikely to hear that you would have a decent occupation, make enough to get by, have a decent marriage and then die at an average age. Instead, you’d either obtain unimaginable wealth or be destined for penury. You would live to a ripe old age, honored by all, or you would be strangled to death and your corpse would be devoured by dogs. But perhaps it is unfair to lay this criticism at the feet of the astrologers. After all, they were simply providing a service to the people, and what their clients wanted was to see themselves in a different life, whether for better or worse. The last thing they wanted to hear was that nothing in their life was ever going to change. So, astrologers obliged them and gave them a window into a different life.

Well, with that we will finally leave Rome behind us and move on to more astronomically advanced civilizations. In the next episode, we’ll start our journey through the astronomy of the last major culture of the Mediterranean, one which has come up in passing again and again over the course of this podcast — ancient Egypt. Relative to the Romans, the Egyptians were a truly ancient civilization, more than a millennium older to the Romans as the Romans are to us today. So next month we’ll have to wind the clock back a few millennia. I hope you’ll join me then. Until the next full moon, good night and clear skies.

Additional references

  • Volk, Manilius and his Intellectual Background
  • Green & Volk, Forgotten Stars