The Renaissance Mathematicus

At the beginning of my post on the rise and fall of astrology I said that a full explanation would run to a full-length book or more and I attempted a short but informative sketch of history. Unfortunately the comments show that in at least one point I was too brief or too confusing and that I had completely ignored another aspect. This is an attempt to plug the holes in the dyke before the flood of ignorance brings the whole structure to collapse.

The first point is by and away most important as it concerns what I see as the main reason for the fall from grace of astrology in the second half of the 17^th century. From the comments it is clear that Rebekah Higgitt is not clear what I was trying to say and if Becky who is a historian of science with the necessary background knowledge is not sure what hope do mere mortals have?

The whole subject hinges on a radical change of metaphysics that evolved over the second half of the 16^th century and the whole of the 17^th and also underlay that which is known as the scientific revolution. The metaphysics that mediaeval Europe inherited from the Greeks and which was renewed in the Renaissance was largely based on the philosophies of Aristotle and to a lesser extent his teacher Plato. Although teacher and pupil differed in many aspects of their thought they were united in their concept of the universe. Their universe was split into two spheres the celestial or heavenly and the terrestrial or earthly. These two spheres were fundamentally different the earthly sphere was constructed from four elements, earth, water, fire and air, was corrupt and subject to change and knew two forms of motion, natural straight towards the earth’s centre and all other motion which was per definition violent. The heavenly sphere was constructed of a fifth perfect element, the quintessence, was harmonious and unchanging and knew only one form of natural, perfect motion, circular. There are more details but they needn’t bother us here. These spheres were separated by the moons orbit and n’e’r the twain shall meet. However the perfect celestial sphere was reflected in the imperfect terrestrial sphere, which was so to speak a badly made model of its heavenly twin.

This situation led to the Renaissance philosophy of micro-cosmos/macro-cosmos or as above so below and the concept of celestial influence. This is the belief that the events in the upper world or celestial sphere influence the events in the lower world or terrestrial sphere and provided the underpinning for the belief in astrology and the acceptance of astrology as a legitimate system of knowledge. During the 16^th and 17^th centuries the developments in natural philosophy slowly dismantled this system of metaphysics and in doing so dissolved the concept of the spheres. The whole universe was constructed of the same substance(s) and motion was the same above and below the moon no longer natural to its sphere but the result of forces (whatever they may be). The final move in this process was Newton’s theory of gravity, which is a universal theory, which means it applies not only on the earth but on and between all the planets and even on comets the jewel in the crown of Newton’s theory.

With the collapse of the difference between the spheres the whole of the micro-cosmos/macro-cosmos philosophy goes out the window and with it the underpinning for astrology. Interestingly this change was at least partial guided by the adoption of two other Greek philosophies those of the Stoics and the Atomists whose metaphysics had never included the difference between the two spheres.

The second point turned up in a discussion in the comments on to what extent the failing empirical confirmation for astrology influenced its decline as an academic discipline. On the whole I don’t think it did. Astrology experienced its high point in European history during the Renaissance and its leading practitioners where largely serious scientist who made significant contributions to the evolution of the natural sciences in the Early modern Period, people like, Regiomontanus and his teacher Peuerbach, Cardano, Phillip Apian, Rheticus, Tycho, Galileo and Kepler. All of them were painfully aware of the empirical deficiencies of astrology and all of them undertook projects to try and remove those deficiencies. These projects were actually the main driving force behind the astronomical revolution and the creation of modern meteorology amongst other things. All of their efforts were in vain and they failed totally in their attempts to establish astrology as an empirical science, however I know of no single case of one of them giving up his belief in astrology. First with a change in the underlying metaphysics and a new generation did astrology loose its academic status.

Jim Harrison one of my regular commentators posted the following comment/ question on my post about the astrology wars:

Arguments about the legitimacy or illegitimacy of astrology in the past may make us lose the opportunity to study the downfall of astrology as a well-documented case of how scientific programs fail. I’m not a historian, though I read a lot; and I don’t have a very clear idea of how it happened during the 17th and 18th Centuries that astrology lost its legitimacy and was relegated to a sad after life in the Metaphysics sections of used bookstores. Its my impression that astrology lost its mojo in England around 1650. I’d like to find an explanation of how and why that occurred assuming I’ve got the dates roughly right. (Goethe began his memoir by summarizing his natal horoscope in his memoir (Dichtung und Wahrheit) in the early years of the 19th Century so maybe I’m assuming that astrology became crank science earlier than it actually did.)

A full answer to his enquiry would be more than book length but I will attempt an outline of an answer here.

The status of astrology in Europe, as we understand it today, and its respectability as an academic discipline has gone up and down like a roller coaster over the centuries since it emerged in ancient Greece in the 5^th century BCE. In antiquity it reached a high point in the second century CE with the codification of its rules and methodology by Ptolemaeus in his Tetrabiblos, which would remain the bible of astrology up till at least the 18^th century.

Following the appearance of Ptolemaeus’ book astrology went into decline along with the rest of the intellectual activities as the Roman Empire collapsed and with it civilisation in Europe. However it should be pointed out that the two most popular and well known astronomy texts in the Early Middle Ages, Macrobius’ Commentarii in Somnium Scipionis and Martianus Capella’s De Nuptiis Philologiae et Mercurii were both as much astrology as astronomy.

As civilisation and urbanisation returned to Europe at the beginning of the High Middle Ages, 1000 to 1200 CE, the renaissance of the sciences did not include astrology as one of the respectable discipline because of the dominance of the Catholic Church in education. For the Church astrology was suspect, and had in fact been strongly criticised by both Augustinus and Thomas Aquinas, because it seemed to contradict the Churches teachings on free will. However in the secular world those rulers on the boarders of the Islamic Empire, in Sicily or Spain, started to adopt the Islamic practice of having court astrologers as political advisors, the evil vizier of Hollywood film, in about the 12^th century. This practice spread and by the 15^th century nearly every European court had its own mathematicus or astrologus to interpret the stars, amongst other things.

Astrology entered the world of higher education with humanism at the end of the 14^th century. The main driving force was the rise of astro-medicine derived from newly available texts from the Hippocratic corpus. In the 15^th century humanist university in Italy and famously in Krakow established chairs for astrology and throughout the next two hundred and fifty years nearly all European universities offered Astrology 101 for medical students taught by the professor for mathematics. Nearly all of the leading Renaissance mathematicians were practicing astrologers, many of them court astrologers. Even Galileo, a practicing astrologer, routinely taught Astro 101 during his tenure as professor for mathematics in Padua. This is not to say that astrology was without its critics, the most extensive criticism of astrology being written by the humanist scholar Giovanni Pico della Mirandola (1463 – 1494), his Disputationes adversus astrologiam divinatricem, which contains all of the standard arguments against astrology still in use today.

Astrology continued to thrive well into the 17^th century but went into a steep decline from about 1650. The big question is why? In general histories of science and cultural histories the standard answer, if they deal with the question at all, is that the new heliocentric astronomy killed off astrology as an academic discipline. This is completely false as any superficial examination of the historical facts immediately shows. As I wrote in an earlier post, Robert Westman famously wrote that there were only ten Copernicans in the entire world between the publication of the De revolutionibus in 1543 and the beginning of the 17^th century and as a historian of astrology correctly pointed out all ten of them were practicing astrologers. Although Kepler, whose heliocentric system was the one that came to be accepted, rejected traditional horoscope astrology as it was practiced in his own times he believed deeply in celestial influence and wrote extensively about his own attempts to create a reformed astrology. So how are we to explain the loss of status of astrology in the 17^th century?

The answer lies in another aspect of the scientific revolution. The Renaissance belief in astrology was based on the micro-cosmos macro-cosmos theory or as above so below. This theory said that the world of the heaven or celestial sphere is reflected in the normal world or terrestrial sphere and that the ability to read the one enabled predictions in the other. This philosophy was inherited from Greek philosophy and was also present in the interpretation of Aristotle that dominated mediaeval philosophy. As Aristotle was replaced as the foundation of natural philosophy by the new scientific philosophy of the 17^th century and disappeared out of the academic realm the micro-cosmos macro-cosmos theory also lost its foothold in academia and with it astrology. Although this process was general throughout Europe it would appear that the reasons for the final loss of respectability for astrology varied from country to country. This has been researched in some countries, such as Britain, but not in others, such as Germany.

In Britain the English Revolution, or Civil War, played a major role in the demise of astrology. In the decades leading up to the English Revolution the social status of astrology was very strong and there was even a Society of Astrologers in London, which boasted many members of the intellectual elite amongst its supporters, such as Elias Ashmole and John Evelyn. During the Revolution astrologers on both sides used their reputations and supposed skills to make war propaganda for their troops, predicting victories and losses that were written in the stars. Following the restitution of the monarchy astrology fell into disrepute because the puritan astrologers had been more successful than the royalist ones. The Society of Astrology was also suspected as being a secret puritan organisation and so the members dissolved the society to remove the suspicion. The fashions in medicine also changed throughout the 16^th and 17^th century and by 1700 at the latest astro-medicine was out and Astro 101 was no longer part of the university curriculum.

In the 18^th century astrology was still alive and well but was no longer part of the academic establishment however in the 19^th century not only astrology by the occult sciences, in general experienced a surprising social renaissance amongst the well heeled and well educated. There were great fashions for things such as spiritualism, theosophy and other forms of mysticism and magic. Perhaps most notoriously in Aleister Crowley’ s Golden Dawn a rebirth of Renaissance hermeticism. I know too little about the subject to say why this occult renaissance took place but Dr SkySkull at Skulls in the Stars has an interesting post on one aspect of the subject.