Some time back the Aussie Anthropoid (aka OOwilkins the Bond Professor) posted a Mr Deity video the theme of which was all of the gifts that he was going to bestow on his chosen people. Lucy compares his list with everything that Zeus is giving the Greeks such as science, medicine and astronomy at which point Mr Deity interrupts to say how much he loves astronomy and to ask if she had seen Larry’s horoscope for that day… Lucy answers “that’s astrology not astronomy” “yer, what’s the difference” asks Mr D. “About 50 IQ points!” Lucy fires back. A truly great line and one that John chose as the subtitle of his post. However one commentator spoiled the joke by pointing out that the Greek’s also practiced astrology to which John gave a short but fairly accurate answer. Inspired by this exchange I have decided to do a series of posts on the intertwined history of the two disciplines of which this forms a sort of introduction.
Words and Concepts:
Today most people have a fairly clear view of the division between astrology and astronomy but from the time of the ancient Greeks up to the 18th century the lexicographical difference between the two concepts was anything but clear. In the first footnote to his brilliant book “ Mathematik und Astronomie an der Universität Ingolstadt im 15. und 16. Jahrhundert” * Christoph Schöner writes that in the Renaissance the words astrologus, astronomus and mathematicus are synonymous, a comment that could equally apply to the preceding two thousand years. In the literature from the Greeks up to the end of the 17th century you will find authors who use astrology for what we consider to be astronomy and astronomy for that which we call astrology. Other authors use astrology or astronomy for both disciplines. In a famous quote Augustinus warns Christians to beware of mathematicians thus demonstrating for some people his anti science attitude. His defenders correctly point out that although he uses the word mathematici he is actually referring to astrologers. This defence is in fact correct and it’s obvious from the rest of the quote that Augustinus is indeed warning his fellow Christians of the dangers of astrology and other forms of divination. However the defence looses some of its strength if one realises that in the time of Augustinus mathematicians and astrologers were one and the same.
For the purposes of these posts I shall be ahistorical and treat the concepts astrology and astronomy as if they had always had clear and separate definitions and in fact those assigned to them by Ptolemaeus in the definitive Greek work on astrology his Tetrabiblos. Here Ptolemaeus writes that the study of the heavens is divided into two disciplines, astronomy, which is the study of the movement of heavenly bodies and astrology, which is the study of their influence. These are the definitions for the two words that I will be using but I should point out that Ptolemaeus himself did not stick to this clear division and in fact mixed up the two terms in his writing like everybody else.
Astrology is more than horoscopes:
Today when people hear the word astrology they, like Mr Deity, think automatically of horoscopes but in fact horoscope astrology is only one aspect, and a comparatively late one at that, of the discipline, which covers a very wide range of celestial influences. In the course of these posts I shall touch upon the origins of horoscope astrology and also deal in some detail with a couple of other aspect of astrology that are not based on horoscopes.
Astrology doesn’t actually exist:
This subtitle is not a sceptical rejection of the claims of astrology but in fact a denial that the discipline astrology exists at all. Anyone who has read so far will probably at this moment think that I have gone insane. I write a post explaining that I shall be writing a series of posts on the history of astrology and now I am denying that it exists at all, how come. The point that I wish to make and it a very important one is that people talk about astrology as if it were a clearly defined single discipline but this is not the case. One thing that makes the study of the history of astrology extremely difficult is that there is not one coherent astrology but literally hundreds of conflicting and even contradictory astrologies. In fact there are almost as many different astrologies as there are authors on the subjects and a large part of the astrological literature consists of the authors explain why their system is the one true correct one and all the others are wrong. What is interesting is that in their disputes mediaeval and Renaissance astronomers will often call upon the same Greek authorities to justify contradictory positions. On the whole I shall again be ahistorical and write as if there were one unified discipline of astrology throughout its history.
Disclaimer: I am not an expert:
Regular readers of this blog will know that my main interest as a historian of science is the evolution of the mathematical sciences between about 1400 and 1750 (I will explain those dates one day). Now nearly all of the practicing mathematicians in this period, at least up to about 1650, were not just astrologers but the wish to reform astrology and set it up on a firm empirical footing was one of the main driving forces of their work so if you really want to understand them as a historian you have to engage with astrology and its history, which over the years I have done. Now if somebody had said to me thirty years ago that I would spend substantial amounts of my time reading astrology books or books about astrology I would have recommended them a good psychiatrist, however that is exactly what I have done in the last years and although I now have a reasonable working knowledge of some aspects of the history of astrology and its practitioners, particularly in the Renaissance I am anything but an expert on the subject. The history of astrology is an incredible complex, multi-dimensional and twisted subject and I’m very glad that people, who are much better historians than I, have devoted their time and considerable talent to it thus enabling me to distil their collective wisdom from their books and papers. What will follow in the later posts in this series are some thoughts and conclusions that have crystallised out of my readings on the subject and are by no means authoritative but I hope will be at least somewhat informative and possibly stimulate the reader into rethinking their own view of the role of astrology in the history of western thought and in particular science.
* If you read German this book, Schreiner’s doctoral thesis, contains in the first 150 pages the best account of the teaching of mathematics in the European mediaeval universities that has ever been written (it’s one of my bibles!).
The Renaissance Mathematicus 
Careful, now: don’t treat astrology as a distinctly separate taxological subject. It must be viewed as an integral part of the quadrivium, and that within the trivium-quadrivium-theology heirarchy, which places this firmly within the Nominalist camp. I’m indebted to Little Rock’s Laura Smoller for the identification of Cardinal Pierre d’Ailly as the planner behind a Roman Catholic strategic plan for the Eucharist as a central plank of their claims for Papal Supremacy which put an end to the Consilium period in the early fifteenth century and gave rise to the Renaissance. His heritage passes through the Bishopric of Cambrai to Erasmus, making conceptual space for Copernicus: the lineal link is through Regiomontanus’s pupil Domenico Maria Novara da Ferrara, as shown by Columbus’ parallel studies of d’Ailly and Regiomontanus as his inspiration for the proof the world is spherical. His ancestors, Gerard Groot (and alongside him, then, the humanist Devotio Moderna of Thomas à Kempis) and Jan van Ruusbroec, and the Victorines running right back to Peter Abelard’s defeated mentor Guillaume de Champeaux at the very birth of the University.
Put in plain terms, the other facets of the quadrivium are mathematics and music – which are the most likely tracks you will find to take you back – and geometry. In my study, I have a hypothesis to prove that d’Ailly’s astrological heir, Jean de Bruges, was in fact Jan van Brugge, known to the rest of us as Jan van Eyck. My problem is that the astrological works of the former were published shortly after the death of the latter, which is not that unusual for the period as it just predates printing: an authors works tended to be copied posthumously as they were hand-copied once the author stops making additions! These are not taxonomically distinct subjects, but reexpressions of a common theme.
So, in a word, you have to distill the scientific heritage from the theological one (working chronologically) or reintegrate it carefully if working back towards the sources: the latter, merged with concepts of the fourteenth-century morale crisis which gave rise to the symbolisms tapped firstly by puritanism, then by the Enlightenment and finally by horror films, none the less has some interesting modern echoes of an apocalyptic nature.
Can I open another track for your examination: that of the de’Medici family. The French have a commonplace piece of knowledge, that on the death of King Henri II in 1559, the readjustment of power left Catherine de’Medicis in power, power she used immediately to take her rival, the late King’s mistress Diane de Poitiers, down a peg or two by forcing her to swap the pretty chateau of Chenanceau with that of Chaumont, a more mediaeval place. Diane never took up residence in the latter, as when she moved in she found the place covered floor to ceiling with astrological workings done by Catherine and her military broker the Constable of France Anne de Montmorency, under the tutellage of an Italian astrologer Ruggieri. What is not known is that when the French archaeological heritage reopened the attics of Chenonceau in 1990, they discovered yet more of the same workings – I was there the day it was discovered and before they decided least said, soonest mended.
The Medici seem to have sponsored a number of astrologers of less controversial origins, amongst them Pico della Mirandola and more closely within the family, Cosimo the Elder. Naturally, the supposed link between astrology and alchemia was essential to a family of medical origins.
Dear thonyc, your writing “Now if somebody had said to me thirty years ago that I would spend substantial amounts of my time reading astrology books or books about astrology I would have recommended them a good psychiatrist, however that is exactly what I have done in the last years and although I now have a reasonable working knowledge of some aspects of the history of astrology and its practitioners,…” encourages me to ask the following question: Did you find anything that could explain why the people where so eager to work on world systems which would give the positions of the celestial bodies with better precision than what was achieved by the medieval ones? Was it, as I would suspect, that they blamed the failure of astrological prophecies to the inaccuracy of their data? (Wouldn’t it be nice to know to what extent modern science owes its birth to superstition?)
Oh very much so, you can read a brief account here
Very instructive, thousand thanks! I have already included piece of your material into the (german) wikipedia article on history of astronomy.