Post-classical history

CHAPTER 15
The Polymaths of the Sixteenth Century

One thing with which the Middle Ages is indelibly associated is belief in magic. But, in fact, the sixteenth and seventeenth centuries were when magical thinking was at its most intense and widespread. At first this seems strange; at precisely the period when most now believe that modern science was being born, the occult enjoyed a remarkable resurgence. Even Sir Isaac Newton, it turns out, was obsessed by alchemy and at the end of the seventeenth century, astrology was still big business. Of course, it still is today.

Hermetism

To find out why magic was so popular during the early modern period, we have to travel back to Florence in 1463. There, Cosimo de Medici (1389–1464) lay dying. He had been de facto ruler of the city for 30 years, his family having made a successful transition from banking to politics. His long administration had seen Florence become the jewel of Italy, its status celebrated by the completion of Filippo Brunelleschi’s magnificent dome on the cathedral in 1461. Cosimo had been a patron of both the arts and literature. He sponsored the humanists who searched out ancient manuscripts and founded the Laurentian Library to house their booty. This library, for which Michelangelo later built the vestibule, already housed 3,000 manuscripts when it opened to the public in 1571, including many of those that first allowed western scholars to enjoy the surviving literature of ancient Greece.1

Before he died, Cosimo wanted to read Plato, whose books had been almost entirely unknown during the Middle Ages. He was unable to understand Greek himself, but he could afford to hire the best scholars to translate newly discovered manuscripts into Latin. During the Council of Constance back in the 1430s, Cosimo had first heard about the philosophy of Plato from a neo-pagan magician. The council had been called to reunite the Catholic and Greek Orthodox Churches so that the Pope would launch a crusade to rescue Constantinople from the Turks. The project fell apart but the meeting of the finest minds of eastern and western Christendom had profound consequences. Among the Byzantine intellectuals at the council was one Gemistus Pletho (c.1355–1452). He was Plato’s greatest admirer, but also a sun-worshipper.2 The young Cosimo de Medici heard Pletho extolling the virtues of neo-Platonism but probably also learned about more esoteric writings.3

Marsilio Ficino, Cosimo’s most gifted translator, had long been gathering together manuscripts of Plato’s dialogues. But the dying Cosimo ordered Ficino to lay aside the work on translating Plato. Cosimo’s agents had discovered a manuscript languishing in the library of a Macedonian monastery. It purported to have been written by the legendary sage Hermes Trismegistus of whom he had, perhaps, heard through Pletho.4

Ficino and Cosimo both believed that Hermes Trismegistus was an Egyptian seer, a contemporary of Moses and the oldest of the prophets of God. In English, Trismegistus translates into something like ‘three times blessed’. Today we hear little about Hermes and might wonder what all the excitement was about. However, during the Renaissance, his writings were thought to contain the long-forgotten secrets of a race of magicians. There were good reasons for believing this. Augustine of Hippo, in a passage otherwise hostile to Hermes, had conceded that he was a great sage, while other Church fathers praised his wisdom and authority.5

Ficino and his contemporaries dated the works of Hermes to about 1300BC, roughly at the time of Moses’s exodus from Egypt as described in the Bible. Ficino took Hermes’s works to be among the original sources that Plato had used to formulate his philosophy, and he also thought them to be fully compatible with Christianity. That meant that the Hermetic corpus, as it was known, was the original pristine theology in which the deepest truths of God could be uncovered. Within it, readers could find intimations of the Trinity, the incarnation and a multitude of neo-Platonic ideas such as the ‘great chain of being’. Most exciting of all, the Hermetic corpus laid out procedures that allowed a magician to compel angels and other benign spirits to carry out his orders.

Ficino was one of the foremost scholars of his age and one of the few who were able to accurately translate from Greek into Latin. He was also a Catholic priest so his interest in ancient magic might seem rather incongruous. Nonetheless, he was convinced that it was possible to harmonise the work of Hermes with Christian theology because he believed that, although Hermes was a pagan, he had enjoyed some glimpse of the divine mind that was now lost. It took Ficino only about a year to produce his translation and he was able to hand it to an ailing Cosimo de Medici shortly before he died. The resulting book was hugely influential for 150 years after Ficino published it.

In Ficino’s translation, this magic attempted to harness the power of the stars and especially the sun. He called the sun ‘the lord of the sky, which rules and moderates all truly celestial things’,6 and revived the old notion that the heavens produce a sound, the music of the spheres. By composing his own astral songs, Ficino believed he could control the power of the stars. His rituals drew on a hotchpotch of ancient traditions including stories about Pythagoras and Orpheus.7 Pythagoras was important because he formed a link in the chain between Hermes Trismegistus and Plato along which the wisdom of Egypt had been transmitted to Athens.

Anyone visiting a library to read an English translation of the Hermetic corpus will probably be disappointed.8 It is mainly in the form of dialogues between Hermes and his son about mystical matters that do not make much sense to the uninitiated reader. The language is heavily symbolic and subject to a multitude of different interpretations. Once Ficino had finished his translations the more difficult task was to figure out what it all meant. This spawned a voluminous literature of commentary and discussion that only the most dedicated of today’s researchers feel inclined to plough through. Then, in 1614, the whole Hermetic corpus was finally revealed to be a forgery. Isaac Casaubon (1559–1614), a French Protestant exiled in England, exploded the myth. In a massive refutation of the errors of Catholicism, he pointed out that Hermes was actually a phoney invented well after the birth of Christ and, furthermore, the apparent anticipations of Platonism and Christianity were simply plagiarism.9 After word of this got around, the Hermetic corpus became something of an embarrassment and scholars quietly dropped it.

The revival of magic set in train by Ficino was carefully couched in terms that made it acceptable to Christians. As long as the subject was confined to discussion among educated priests and bored aristocrats it caused little stir in the outside world. The most visible result may have been the proliferation of magical sigils and symbolism in art such as in Botticelli’s paintings the Mystical Nativity and Primavera. Pope Alexander VI (1431–1503) had his private apartments in the Vatican decorated with frescos of astrological figures. These included a picture of Hermes Trismegistus himself, in conversation with Moses and the Egyptian goddess Isis.10 However, the influence of Hermes went well beyond the safe bounds of Italian high society. With the backing of such esteemed scholars as Ficino, magic now went mainstream. It was no longer the preserve of strange old women and renegade priests. Couched in the elegant Latin of the humanists, the Hermetic corpus was a licence to reinvent astrology, alchemy and other forms of occult knowledge. Soon it seemed that almost every European intellectual was infected with the magical bug, labouring under the impression that the Hermetic corpus opened up exciting vistas of forgotten wisdom.

John Dee Reforms Astrology

Among the biggest beneficiaries of the revival of the occult was astrology. During the Renaissance, astrology’s problem was not official censure but the inconvenient fact that it did not work. Almost everyone agreed, whether they supported astrology or not, that the success rate of even the best practitioners left a great deal to be desired. Among those earnestly seeking a solution to this problem was the English magus John Dee (1527–1609).

Dee was a product of Cambridge University. Humanists – led by Erasmus himself, who had briefly taught there – saw off medieval philosophy and were propagating the new learning. Greek, Hebrew and mathematics were the subjects of the day. Dee himself taught Greek at Trinity College, founded in 1546, and benefited from the new surge in maths teaching brought on by the reform of the university syllabus in 1549. Even so, as he arrogantly explained in a short autobiography he wrote late in life, Dee quickly outgrew the ability of anyone at Cambridge to teach him and studied on his own. He travelled throughout Europe, delivered lectures at the university of Paris on geometry and hobnobbed with the most admired natural philosophers of the day.11 He returned to England determined to launch a thoroughgoing reform of astrology and place it on a firm scientific foundation. It never seems to have occurred to him that astrology might not work at all, but that was not his fault. The art of prediction was completely consistent with Dee’s worldview and offered such great benefits that it was quite rational for him to devote himself to perfecting it. Most attacks on astrology from this time are religious rather than scientific. Countering the naysayers, some religious thinkers, like Luther’s right-hand man Philipp Melanchthon (1497–1560), were extremely enthusiastic about astrology. He spent many years lecturing on it at Wittenberg University, where Luther was based.12

Dee’s astrological agenda harnessed mathematics to astronomy so as to provide a scientific explanation of how the stars and planets influenced events on earth. He began by postulating that each planet gave off rays that imparted certain properties to whatever they struck. As the planets moved around the sky, the relative intensities of these rays on earth changed.13 This explained the variety of astrological effects and why where you were born was as important as when. Thus, if the rays from Jupiter and Mars were especially strong at the moment of your birth, then you would obtain jovial and martial characteristics – that is, you would be jolly but prone to violence. Dee wanted to mathematically calculate the force of the rays from each of the individual planets at a particular place and time to provide an exact horoscope. However, he faced some formidable problems. He needed to know the relative distances to the planets more accurately than was possible at the time. He also could not assume that the rays emanating from each planet were of equal strength. This meant he was unable to calculate their intensity once they reached earth. Finally, he realised that the angle at which the rays struck the earth had a profound effect on how powerful they were. This is most obviously the case with the heat from the sun, which warms the equator (where it is directly overhead) far more than the Arctic region (where it never rises very high in the sky). The necessary calculations were beyond Dee, however, and he lacked the patience to devote enough time to such a complicated problem.

Dee’s attempt to reduce astrology to mathematics showed that he was thinking along the right lines. But as a scientific venture, it was always doomed to failure because his underlying theory was wrong and he had no reliable way to experimentally verify his hypothesis. Not many astrologers shared Dee’s passion for a reformed astrology, but they all realised that it was essential to use the very best methods available to plot the movements of the planets. This demand for accuracy provided a major market for astronomers’ tables and helped drive their standards up. In turn, having the ability to master the complicated geometry necessary to predict the position of the planets improved the professional status of the astrologers themselves. They were no longer treated with the suspicion that had clung to them in the Middle Ages. In the sixteenth century, astrology enjoyed a boom and its practitioners became celebrities. Girolamo Cardano, although virtually forgotten today, was the most famous astrologer and physician of his time. His reputation spread as far as England and even over the border to Scotland. In fact his name was anglicised to Jerome Cardan, which is remarkable in itself. It means that he was as famous as his contemporaries Michelangelo and Raphael, both of whom were also re-christened with English names.

The Life of Jerome Cardan

Cardan was born in Pavia in 1501 amid the turmoil of early-sixteenth-century Italy.14 He spent much of his childhood in Milan living under French occupation after Louis XII (1462–1515) had invaded in 1499. The city was briefly liberated in 1512 and plague finally drove the French from the city in 1522. Jerome’s family was genteel but not wealthy. The shortage of money when he was a child instilled in him determination to get rich and famous as quickly as he could. His horoscope gave him some measure of encouragement but also a dreadful warning. It predicted that he would become extremely well known but would die before he reached old age. ‘There were stars which threatened my death from every aspect’, he wrote, ‘which all declared would be in my 45th year.’15 From his earliest youth, Cardan believed he was a man pursued by the fates to succeed, burn brightly and quickly fade.

His father, Favio, was a successful lawyer who wanted his son to follow in his footsteps. But Jerome, fascinated by philosophy and mathematics, decided that he would become a doctor. Favio himself had dabbled in these subjects when he prepared the first printed edition of the textbook on optics by John Peckham, the thirteenth-century archbishop of Canterbury.16 Perhaps that is how Jerome knew there was no money in natural philosophy. There were a series of blazing rows over the matter before Favio finally relented and allowed his son to study medicine at the university of Pavia.17 Although no money was available to pay for the fees or Jerome’s living costs, he was already an accomplished enough mathematician to earn his keep by hiring himself out as a tutor. Jerome had another skill that helped him to make ends meet – he was a gifted gambler.

Despite the disapproval of the church, Italy was awash with gambling dens where men wagered whatever they could afford. Jerome Cardan had an enormous advantage over almost all of his fellow gamblers – he understood the concepts of probability and odds. While playing with dice is a matter of luck, those who know what the odds are can be careful only to wager substantial amounts when the odds are in their own favour. There was no ‘banker’ with a built-in advantage, so if the skilled gambler’s opponents had a less sure grasp of the odds than he did, then he could fleece them. The science of probability did not even exist at the time – Cardan invented it. He was the first to decree that all probabilities can be shown as fractions between zero (for impossible) and one (for a certainty). Thus the probability of a coin landing heads-side-up is ½ or one in two. It tells us something about western civilisation that this most vital field of mathematics was first developed by a student trying to raise enough money for his bar tab. Even so, Cardan’s book on the subject was not published in his lifetime and by the time it was, others had established priority.18

In 1526, Jerome Cardan qualified as a physician and rode back to Milan to start what he hoped would be a medical career. Unhappily, the Milanese College of Physicians decided to reject his application for membership. Without the College’s approval, Cardan could not work in Milan and so had to build up his reputation as a healer in the provinces. He was bitterly disappointed by the snub and spent many years attempting to gain admission to the College until, in 1539, he was such a celebrated doctor that they had to let him in.19

Cardan’s success as a physician was almost entirely down to his philosophy of non-intervention. His peers tortured their patients with a gruesome regime of bleedings, purgatives and potions guaranteed to weaken the constitution of even the hardiest soul. As we have already seen, doctors of the time based their theories on a mixture of Galen and the Arabic medical writers, with a dose of natural magic and plenty of guesswork. Merely by sporting a professional qualification, doctors could demand hefty fees for accelerating the demise of their clients. This is surely the reason that so many people put their trust in the village wise women and the intercession of the saints. Both were much less likely to kill them before they had a chance to get better on their own.

Whether by intuition or genius, Cardan gave his patients a chance to heal themselves. Rather than the constant round of prescriptions and bloodletting, he suggested a healthy diet and plenty of rest. In this way, he gained a reputation far beyond the borders of Italy as a doctor without parallel.

In 1551, John Hamilton (1511–71), the archbishop of St Andrews in Scotland, was suffering from failing health. Hamilton was not only the leader of the Church in Scotland. He also wielded considerable political power during the minority of Mary Queen of Scots (1542–87), who was just nine years old at this time and safely exiled in France. The archbishop suffered from a lung condition, very possibly asthma, which had defeated the efforts of all the physicians in Scotland. In desperation, he called for Cardan and offered to meet him in Paris where Hamilton expected to travel on diplomatic business. With his affairs in order, the Italian very much liked the idea of an all-expenses-paid expedition to France and set off as soon as he could. He had got as far as Lyon when he learned that Hamilton had not, in fact, left Scotland and was begging him to travel all the way to Edinburgh. A substantial purse of gold convinced Cardan that he could risk the journey and he reached Hamilton’s palace in the summer of 1552.20 Dismissing the assembly of physicians arguing over Hamilton’s treatment, Cardan launched the archbishop into a detailed regimen of milk, rich food and relaxation.21 The new approach worked and the patient began to improve. He lived for another twenty years (before being executed by Scotland’s new Protestant rulers) and always attributed his longevity to Cardan.

The case sealed Cardan’s status as Europe’s foremost doctor. Even before he left Scotland, a messenger arrived from London asking him to come and treat the sickly king of England, Edward VI. Obeying the summons, Cardan found that it was his skill as an astrologer as much as his medical talents that led the English court to consult him. He met John Dee and discussed the properties of a magical gem, as well as producing a chart showing that the king’s stars would grant him marriage and a long life.22 Cardano later claimed that his actual horoscope for Edward VI had shown that the king had just months to live (which in fact he did), but that he lied about this in order to avoid provoking an affair of state. Not everybody was convinced by this, especially as he had already published the king’s false horoscope. In an unfortunate coincidence of timing, it appeared shortly after the young man had died.23

Astrology was Cardan’s lifelong passion. He called it ‘the most lofty of the branches of knowledge because it deals with celestial things and with the future, awareness of which is not only divine but also very useful.’24 Medical practice merely provided an income and a secure reputation that allowed him to indulge his real interest.

Alert readers will have already noted that Cardan did not die at the age of 45 as his horoscope had demanded. Clearly, there was a problem with the prognostication, albeit an extremely welcome one. Like John Dee in England, Cardan launched a project for the reform of astrology.25 However, his plan was completely different from Dee’s attempt to provide a mathematical basis for the art. Despite being the better mathematician, Cardan adopted an empirical approach. Perhaps he was well aware of the shortcomings of Dee’s idea and realised that the calculations required to plot the influences of all the planets would just be too difficult. Instead, he gathered together the horoscopes of as many people as he could find and compared the predictions to how their lives actually turned out.26 This was a difficult business in itself, because he needed accurate information on when and where all his subjects had been born. He hoped to be able to collate the horoscopes so that he could formulate some rules about the ways in which the influences of the planets interacted. His collection of horoscopes went through several editions, some printed by the publisher of Copernicus’s Revolutions of the Heavenly Spheres, and was a commercial success.27 But, needless to say, Cardan’s great venture failed scientifically and as astrology fell from favour among scholars, it has tended to be written out of history. What is most interesting about the efforts of Dee and Cardan to restructure astrology is how closely they both conformed to the methodology of science as we would recognise it today. The twin tasks of gathering data and generating mathematical theories are both essential parts of almost all modern science. It is ironic that the first concerted attempts to do this were performed in a subject that is no longer considered scientific at all.

Among Cardan’s collection of horoscopes was one he prepared for Jesus Christ. He must have known how much trouble this had got Cecco D’Ascoli into and it was rumoured (falsely) that the medieval magus Guido Bonatti had been burnt at the stake for the same reason. Nonetheless, Cardan made no effort to conceal what he had done, and even included a lengthy discussion of Jesus’s horoscope in his edition of Ptolemy’s book on astrology.28 This bravado would later bring great misfortune upon him.

Cardan and Tartaglia

In the 1540s and 1550s, Cardan was at the height of his fame and influence. He published on any subject that interested him and wrote a considerable number of bestsellers. His most successful works were two volumes of what we might call ‘popular science’ calledOn Subtlety (1550) and On Variety (1557). They contained a smorgasbord of interesting factoids as well as numerous inventions cooked up by Cardan’s resourceful mind. A few of these are still in use today. For example, buried somewhere in the engine of modern cars is a device called a ‘cardan joint’ that allows a spinning driveshaft to bend. Cardan was also familiar with impetus theory,29 which he used in many applications, and he accepted the possibility of a vacuum.30 On Subtlety is one of the earliest books in which we find Archimedes (287–212BC) raised to the highest status among the ancient sages. Cardan’s discussion of his writing probably did much to bring it to a wider audience.31

Archimedes’ work was more advanced than that of any other Greek mathematician. Unfortunately, this meant that it flew over the heads of many of his contemporaries and even some of those who came long after. We tend to remember Archimedes for crying ‘eureka!’ (Greek for ‘I’ve found it!’) and leaping out of his bath. The story is probably apocryphal and refers to his discovery of the law of buoyancy. The law states that any object dropped into water will displace an amount of liquid equal to its own weight. If the object has a lower density than water, then it will not displace enough water to cover itself completely and so will float. At the end of his life, Archimedes designed some impressive military equipment to defend the city of Syracuse from the Romans during the Second Punic War in 212BC. Despite the reported use of burning glasses and a giant hook to sink the Roman galleys, the city eventually fell to them and Archimedes was one of the victims of the slaughter that followed.32 Many of his mathematical works had been translated into Latin during the Middle Ages, but it was not until the sixteenth century that they were intensively studied.33

Cardan’s most significant book was of a more academic hue – a guide to advanced mathematics, which he called The Great Art (1545). This contained the first published solutions to cubic and quartic equations, the former of which occasioned an almighty row with a fellow mathematician, Niccolò Tartaglia (c.1499–1557) who claimed that he had found the answer first.

Tartaglia was born in Brescia and was brought up by his mother after losing his father at an early age. He barely made it into his teens himself. In 1512, the French stormed the city. Many civilians, including Tartaglia and his mother, sought sanctuary in the cathedral but the French were no respecters of the holy building. They mutilated the boy and left him for dead. One blow split his jaw but by some chance he survived. His mother nursed him back to health but his injuries left him with a permanent stutter. Rather than be ashamed of this, he named himself ‘the stutterer’, which in Italian is Tartaglia.34 We do not even know what his real family name was.

Although he was not ashamed of his speech impediment, Tartaglia always had a chip on his shoulder over his lack of formal education. He was self-taught and never mastered the elegant Latin that his peers thought was essential to intellectual discourse. Nevertheless, he was a mathematician of genius and was soon earning his living teaching others the subject. In 1537, he moved to Venice and published his first book called New Science. This dealt primarily with the mathematics of cannon balls. At the time, Venice was preparing to do battle with the Turks who were following up their conquest of Constantinople by trying to achieve mastery of the rest of the Mediterranean. New Science, dedicated to the Venetians’ general, was Tartaglia’s contribution to the struggle. In the book he showed that a cannon ball should move with a curved trajectory, at least for part of its flight. Later on, in his Questions on Diverse Discoveries (1546), he demonstrated that the path of a projectile should be a curve throughout.35

In 1539, Cardan invited Tartaglia to visit him in Milan. During his stay, Tartaglia imparted the secret of how to solve cubic equations to Cardan on condition that he kept the method to himself until it was published. Understandably, Tartaglia wanted to reveal the discovery in one of his own books. In the meantime, he had other projects on the go, including his 1543 edition of the medieval Latin translation of the works of Archimedes. This book finally brought the achievements of the great Greek mathematician to a wide audience and is probably how Cardan himself came to hold him in such high esteem. Tartaglia strongly implied that he had translated Archimedes from the Greek himself. He wanted to appear as well-educated as the cultured humanists but the plan backfired after he was found out.36 And when he had not published his solution of cubic equations after six years of procrastination, Cardan lost patience. He included cubic equations in The Great Art, much to his now-rival’s fury.37 Tartaglia died twelve years later in Venice, still convinced he never received the respect that was his due.

Cardan’s Family Problems

The last fifteen years of Cardan’s life were filled with one terrible misfortune after another. It was his sons who were to bring down disaster upon him. His elder son was called Giovanni and the younger Aldo. He also had a daughter Chiara who, at least, caused him no trouble beyond the cost of her dowry. This expense, which Cardan was still talking about decades later, earned him a valuable confidant in his son-in-law.38 Sadly, to her father’s lasting regret, Chiara had no children.

Aldo appears to have been something of a psychopath. He was a thief and a violent ruffian, continually being arrested for his crimes. Cardan was now rich and spent a fortune paying fines and bail on behalf of his dissolute son. Eventually his behaviour became too much even for this most indulgent of fathers. Aldo was expelled from the family house and then exiled from the city itself.39

On top of these family worries, Cardan had all the usual problems of fame. When he became a lecturer at the university of Bologna, his colleagues were even more envious of his extramural success than academics of today would be. They kept up a constant campaign of sniping, tale-telling and poaching of his students.40

His books did not please everyone either. On Subtlety provoked what one modern scholar has called ‘the most vitriolic book review in the annals of literature’.41 The humanist Julius Caesar Scaliger (1484–1558) wrote a 900-page tirade, twice the length of On Subtlety itself, berating Cardan for every aspect of the book. Scaliger was especially outraged about the elevation of Archimedes above Euclid and Aristotle. ‘You have put a builder [Archimedes] before Aristotle, who was no less knowledgeable in these arts’, he fumed, continuing: ‘After Archimedes, you have put Euclid as if the light after the lantern.’42 The rebuttal proved almost as popular as its target with the book-buying public who then, as now, liked nothing more than a good literary spat.

Cardan decided not to rise to the bait and Scaliger was disappointed not to receive a reply in kind. The silence of his target began to unnerve him and he allowed himself to be convinced that Cardan had read his book and died of shame. Overcome with remorse at causing the death of his adversary, Scaliger composed a gushing obituary. ‘Cardan’, he wrote,

in addition to his profound knowledge of God and nature was a consummate master of the humane letter … A great man indeed! I affirm that the man who would venture to compare himself to Cardan may well be regarded as one who is lacking in all modesty.43

Luckily for his own reputation, Scaliger heard that Cardan was very much alive before his panegyric was published.

Cardan had to endure a far more painful experience than wounds to his pride. His son Giovanni had unwisely married a shrewish woman whose family constantly tried to extort money from his wealthy father. So Cardan must have been shocked but hardly surprised when word was sent to him that his daughter-in-law lay dead from poison and his son was under arrest as the prime suspect. Here was a crime that it was beyond the means even of Cardan to make good with a hefty bribe. The case came to trial in the Palazzo Marino, now Milan’s city hall, in February 1560. Giovanni claimed that he had used his medical expertise to manufacture a toxin with which he had laced a cake he baked for his wife. He also admitted that his incompetence was such that he had failed twice in the scheme before finally managing to do away with her. After the confession, the trial judges had only to decide on the sentence. That would have been a formality but for Cardan’s celebrity and civic importance. He launched a heartfelt and eloquent appeal for his son’s sentence to be commuted to exile or life imprisonment:

Although I brought forward many arguments and their like, it availed naught except in so far as it was decreed by the court that if I should be able to come to terms with those who had brought the charge against him, his life would be spared. But the very indiscretion of my son forbade this. For he had boasted of riches which I did not possess and the accusers tried to exact what did not exist.44

No agreement could be reached and Giovanni was executed in his prison cell. Cardan never recovered.

Even then, his suffering was not over. In 1570, he was arrested by the Inquisition in Bologna. The details of the charges are unknown but probably resulted from the jealousy of his colleagues at the university. The Inquisition, like many other official organisations of oppression, relied very heavily on denunciations from informers to do its job. This provided an easy method of revenge for anyone who wished to take advantage of it. In Cardan’s case the sheer volume of his writing, his relatively unguarded pen and, of course, that horoscope of Christ provided plenty of material for the tribunal to wade through. It seems, though, that they could not be bothered to do so. After a few weeks the prisoner was released on bail and eventually he must have been acquitted, for we hear nothing of any trial, let alone a conviction.45

At least this marked the end of his troubles. Cardan travelled to Rome and petitioned the Pope over his treatment by the Inquisition. The outcome was a papal pension and a respectable retirement until his death in 1575, 30 years later than his horoscope had predicted. He spent his last four years writing his autobiography, The Book of My Life, through which we now know so much about him.

The astounding breadth of Cardan’s interests makes him a true renaissance man. His Great Work on algebra taught Europe all the new advances in the subject which Italian mathematicians had been working on. His medical practice was both humane and successful. He tinkered and invented constantly and, unlike some authors, he made no effort to keep his good ideas to himself. His obsession with astrology was based on a desire to place this useful art on a firmer footing than hitherto. Perhaps his careful collation of horoscopes had the unintended but beneficial consequence of demonstrating that the stars have no effect on our lives after all. Above all, Cardan and Dee show us that the boundary between the occult and the scientific in the sixteenth century was both porous and indistinct.

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