Causes of the Bubonic Plague

The Bubonic Plague's first appearance in medieval Europe from 1348-1351, and it was terrifying. At least one-quarter to one-third of the population died in those few years; entire villages were depopulated, and no country was untouched.

King Philip VI of France asked the University of Paris to determine the cause. Forty-nine members of the medical staff studied the matter and wrote the Paris Concilium.

They produced more than one theory of why humans were suffering from it, while maintaining that the plague was too mysterious for human beings to ever truly understand the origin. They drew from the available authorities: Avicenna's work on pestilential fever, Aristotle's Meteorology on weather phenomena and putrefaction, Hippocrates' Epidemics on astrology in medicine.

Their theories:

—The Concilium followed Aristotle's idea that a conjunction of Jupiter and Saturn was disastrous. Albertus Magnus believed a conjunction of Jupiter and Mars would bring plague. A conjunction of Saturn, Jupiter, and Mars took place in 1345 right after solar and lunar eclipses, under the sign of Aquarius, compounding the disastrous effects of the planets. Jupiter was sanguine, hot and wet—the worst combination that would lead to putrefaction.

—Another possible cause was poisonous gases released during earthquakes. Disadvantageous conjunctions of constellations produced winds that distributed gases rising from rotting carcasses in swamps. The poisonous vapors would be inhaled and go straight to the heart (they thought the heart was the organ of respiration), and then cause the body's vital organs to rot from the inside.

—There was also the possibility of God's punishment for man's wickedness.

Of course, there was no reason to believe that these causes were mutually exclusive.

The plague was devastating, and also didn't end in 1351. It remained endemic to Europe, as I'll discuss next time.

The King of Poisons...

...and the Poison of Kings are two nicknames given to arsenic.

As early as the Bronze Age, the mineral arsenic was added to bronze to make it harder, although isolating it chemically and understanding it as an element was not recorded until 815CE by Jābir ibn Hayyān. Albertus Magnus (pictured) isolated the element arsenic from arsenic trisulfide by heating it with soap in 1250.

Non-pure forms of arsenic were known much earlier. Dioscorides during Nero's reign described arsenic as a poison in the 1st century, noting its odorless and tasteless and colorless properties, making it ideal to mix with food or drink. Arsenic poisoning's side effects were similar to food poisoning, so immediate detection was unlikely. A sufficiently large dose, however, produced violent cramping, diarrhea, vomiting, and death.

You could also use smaller doses on a victim over time, leading to headaches, mental and physical fatigue, confusion, hair loss, and paralysis. The preferred form of arsenic was white arsenic, arsenic trioxide, whose fatal dose was the size of a pea.

Arsenic compounds exist everywhere: in groundwater and (as a result) in trace amounts in plants. Organic arsenic compounds can be found in low levels in seafood. Lettuce, kale, mustard, and turnip greens store arsenic in their leaves. Beets, turnips, carrots radishes, and potatoes store arsenic mostly in their skins. There is also arsenic in the plants of tomatoes, peppers, squash, cucumbers, peas, beans, corn, melons, and strawberries, but not the parts that we eat. (Apple seeds contain. cyanide, but that's another story.)

The Borgias of Italy—including Rodrigo Lanzol Borgia, who became Pope Alexander VI in 1492, and his son Cesare and daughter Lucrezia—were known for their use of arsenic for political and financial advancement. They would take advantage of legal loopholes to appropriate the estates of certain men after killing them with arsenic-laced wine.

In fact, poisoning became so common that Italian court documents show plenty of cases in which we find the details of the poisoning:

The poisoner made appointments and had set prices, the client named the victim and a contract was made, and the poisoner was paid when the job was done. [link]

There was also a woman named Giulia Toffana around this time who made arsenic-laced cosmetics, so the victims could be induced to poison themselves.

If you suspected you had been poisoned, what would you do? Probably go to an apothecary to buy a cure. We'll talk about medieval apothecaries next time.

Thomas Aquinas

I suppose if we wanted to find a Christian parallel to Maimonides, Thomas Aquinas would be an obvious choice. Born into the aristocracy, noted for his learning and devoutness, his writing blending previous scholarship and building on it with impressive arguments backed up by Scripture and reason, his writings becoming foundational for what came after—no wonder he was nicknamed Doctor Angelicus ("The Angelic Doctor").

He was born in 1225 in the town of Aquino. His father was Count Landulph of Aquino, his mother Countess Theodora of Teano; he was related to the kings of Aragon, Castile, and France, as well as to Emperors Henry VI and Frederick II. A biography written a generation after he died claims that a holy hermit predicted to a pregnant Theodora that her child would become unequalled in learning and sanctity.

His education began at the typical age of five, with the Benedictines of Monte Cassino (his father's brother Sinibald was the abbot there from 1227-1236). Some time between 1236 and 1239 he was sent to a university at Naples where he would have first learned about Aristotle, Averroes, and Maimonides. Here he also came into contact with a Dominican preacher. The Dominicans had been founded 30 years earlier and were actively recruiting.

When he was 19 years old, Thomas announced that he wished to join the Dominicans, which displeased his "Benedictine-oriented" family. It displeased them so much that, while Thomas was traveling to Rome on his way to Paris to get away from the family's influence, his brothers (at his mother's request) kidnapped him. He was forced to stay in his parents' castle for almost a year, spending the time tutoring his sisters.

Attempts to dissuade him from the Dominicans became more desperate. His brothers sent a prostitute to seduce him. He fought her off with a burning log, then fell into a mystical trance and had a vision of two angels granting him perfect chastity. (They also gave him a "girdle of chastity" that now resides in Turin.) His mother, seeing that he would not change his mind, and not wanting to endure the embarrassment of allowing her son to join the Dominicans, she arranged for him to escape his home in 1244. He went to the University of Paris where he probably studied under Albertus Magnus. Because Thomas was quiet, his fellow students ridiculed him, but Albertus is supposed to have told them "You call him the dumb ox, but in his teaching he will one day produce such a bellowing that it will be heard throughout the world."

In 1256 he was appointed regent master in theology at Paris and began writing the first of his many theological works, Contra impugnantes Dei cultum et religionem ("Against Those Who Assail the Worship of God and Religion"), defending the mendicant orders.

His reputation as a theologian and teacher/preacher grew so much that he was granted the Archbishopric of Naples in 1265 by Pope Clement IV, but he turned it down. In the yard that followed he would have the time to write one of his greatest works, the Summa Theologica.

And this is where we come back to the comparison with Maimonides: despite the groundbreaking nature of his writing, which became foundational for much of what followed, he was not without his detractors. Some of his conclusions clashed with accepted thought from previous religious writers. To be able to discuss that, we should look at two other philosophers: Aristotle and Averroes. Stay tuned.

The Alchemist

Albertus Magnus and a hermaphrodite
from Symbola aureæ mensæ

We haven't talked about Albertus Magnus since his birthday last year. We really should address the subject for which he is usually known by people who don't know anything else about him: alchemy. Unfortunately, the evidence that he knew any alchemy comes from legends and documents that accrued to his reputation after his death. In fact, his own words are interpreted to deny the possibility of producing something by magic. He wrote ars non potest dare formam substantialem [Latin: "Art alone is not able to make a substantial form"]. Later generations, amazed by his vast knowledge, attributed many writings on alchemy to him. In the absence of any other authorial data, they are now attributed to "pseudo-Albertus Magnus."

There is, for instance, a legend that he managed to transform simple metal into gold, using the Philosopher's Stone. Supposedly, he gave the Stone to his pupil, Thomas Aquinas, prior to Magnus' death. The legend fails to take into account that Aquinas died six years before Magnus. The legend further states that Aquinas destroyed the Stone, fearing a connection with less-than-divine powers. This is recorded in a 1617 work on alchemy called Symbola aureæ mensæ [Latin: "Symbols of the golden table"], by Michael Maier. It is also said that he changed the weather of a winter day to a warm spring day with flowers blooming so that a party could be held outside.

He is also credited (supposedly according to eyewitnesses) with having created an automaton in his laboratory that could speak and perform menial tasks.

As for writings that we can firmly attribute to him, there is little there about alchemy. His De mineralibus [Latin: "Concerning minerals"] alludes to the occult power found in stones, but never explains what those powers might be. His chemical experiments seem to have led to the discovery of arsenic and silver nitrate.

His commentaries on Aristotle, and his ability to blend Aristotelian logic with Christianity, as well as his various (legitimate) experiments, gained him such a reputation for intelligence that it is not surprising that future authors would assume he achieved magical results.

Father of Arab Astrology

Abu Ma'shar, from his Introduction to Astronomy

Albertus Magnus, Robert Grosseteste, Geoffrey Chaucer—well-known names from the Middle Ages denoting a Dominican scientist, a university scholar and administrator, and a courtier and poet. One thing they had in common, besides a love of learning, was their attention to the art of astrology. And through their interest in astrology, they were all influenced by a 9th century Arab known in the West as Albumasar. His full name was Abu Ma'shar Ja'far ibn Muhammad ibn 'Umar al-Balkhi (787-886), and he was one of the most respected figures in the history of astrology.

Abu Ma'shar was of particular interest to Western Europe because he was a source for knowledge of and commentary on Aristotle when his writings reached Europe in the 12th century, brought back by the Crusaders. He offered so much more, however. His work blends knowledge of Greek science with Islamic doctrine, Persian chronology, Mesopotamian astrology, and hermetic traditions from Anatolia. He presented a unified approach to the knowledge of several cultures that lent weight to his work.

For instance, he uses the Biblical Flood as the focal point of his astrological tables. He calculates it at midnight on Thursday to Friday, 17-18 February 3101 BC. This date was not arbitrary, nor was it an indication that Abu Ma'shar believed in a short-lived Earth. He chooses the date because it is the start of the Hindu Kali Yuga (the "age of vice"; the last of four phases the world will go through). His knowledge and acceptance of Hindu chronology and its "Great Year" (composed of 360,000 years) is further shown when he calculated a grand conjunction of planets in 183,101 BC, and again in 176,899 BCE.

The Middle Ages loved "unified theories" that could reconcile different traditions to enhance understanding. Abu Ma'shar argued for the superiority of his chronological calculations because he made the year out to be 365.259 days long. Why was he so enamored of this number? Because "259" he explained was the minimum number of days for human gestation (8.6 months). It was obvious to him that he was onto something!

Unlike the hostility experienced by astrology from the University of Paris and others, who felt it was a way to contravene God's plan, or to know what should remain unknowable, Abu Ma'shar was able to give his astrology a veneer of respectability by acknowledging Islamic religious doctrine.

Albertus Magnus & Astrology

Since the last two days have been about reconciling opposing views, and since today is the anniversary of the death of Albertus Magnus, it would probably be a good time to talk more about him.

Albertus Magnus (c.1200-1280) has only been mentioned so far in the context of rainbows, but he was involved in so much more than that. A German Dominican who became provincial of the order in 1254, he became so widely known for his learning that the term Magnus (The Great) was attached to his name in his lifetime by contemporaries such as Roger Bacon (also mentioned in the rainbow entries, as well as here). Although in the future the Dominicans would be nicknamed Domini canes (dogs of the Lord) and be put in charge of rooting out heresy, Albertus would actually spend part of his life writing to defend ideas that were considered heretical.

Most of the charges of heresy were coming from the University of Paris. The University issued a series of Condemnations between 1210 and 1277, condemning the teaching of ideas they considered heretical. Paris had no authority to universally condemn these teachings, however. In a twist that might seem very modern, this left other universities open to excellent marketing opportunities. The University of Toulouse invited students with "Those who wish to scrutinize the bosom of nature to the inmost can hear the books of Aristotle which were forbidden at Paris."

Attacking Aristotle was one way to raise the ire of Albertus. He had written commentaries on all available works of Aristotle, bringing that classical author more fully into the realm of accessible discussion. When Paris condemned the teaching of Aristotelian astrology as a threat to the notion of free will, Albertus had to get involved by writing the Speculum astronomiæ (Mirror on astronomy).* In this work, Albertus explains (using Aristotle's model of the heavens, of course), how the study of astrology and its predictive ability does not contravene God's Will or Free Will.

The order of the Heavenly Spheres

Between God's divine Will and human beings are the nine spheres of the heavens. As God's Will passes through each of the celestial and planetary spheres, it is tainted by exposure to those un-divine substances, just as water flowing down a stream can erode the banks and pick up silt. This has two results. One is that what we perceive in our study of astrology here from Earth is altered, meaning we are not looking directly at and anticipating God's intent for us. The other result is that, because the divine influence has been tainted or diluted by exposure to corporeal bodies, its influence is now corporeal; that is, it may affect our bodies, but not our souls. Astrological influence could make a man envious or prideful or lustful, and many people are content to just follow their impulses, but we have the ability to refuse to act on these impulses.

For Albertus, studying astrology helped to forewarn us about the influences that filtered down through the heavens, and gave us a chance to resist them. The Speculum became a central argument in favor of astrology for centuries, claiming that astrology helped us to understand and perfect our use of Free Will.

*There are numerous medieval works ascribed to Albertus Magnus with little proof, so modern scholars are cautious about claiming authorship; the Speculum has been disputed, but recent scholarship has found sufficient evidence to feel comfortable to claim it was by Albertus.

The Rainbow Connection

Check this out, then come back.

Theodoric (or Thierry, or Dietrich) of Freiberg (c.1250-c.1310) was a Dominican, a philosopher, and a physician. His name is often written with the title magister (master), so we know he had an advanced university education, almost certainly at Paris. In 1293 he was named Provincial of the Dominican Order, Albertus Magnus' old post.

Freiberg's description of the geometry of the rainbow.

We have 21 works written by him, although a list of works by Dominican authors compiled in 1330 lists 31 under his name. Somewhere between 1304 and 1310, Theodoric produced De iride et radialibus impressionibus (Concerning the rainbow and impressions of radiance). In it, he presents the correct explanation for the rainbow. He explains the primary rainbow, the secondary rainbow and why the colors are reversed, and the path light takes to make the rainbow.

That last is important, especially if you've read the link I gave you above and are aware of the competing theories for refraction and reflection, and the place of water droplets versus clouds. Freiberg accurately describes how the path of sunlight is refracted when it enters the droplet, reflected off the other side of the droplet, and refracted again when it leaves the droplet and becomes visible to the observer. Freiberg determined much of this by experimenting with glass spheres filled with water, an extraordinary act in itself in the history of scientific experimentation.

Perhaps, however, the mechanics of the rainbow was an idea whose time had come. In one of those examples of synchronicity that crop up in history from time to time, there was another scientist who came to some of the same conclusions as Frieberg. His name was Kamal al-Din al-Farisi, and he and Freiberg had no contact—although they did have one thing in common: they both knew the 11th century seven-volume work called The Book of Optics by Ibn al-Haytham. But that's for another day.

Chasing Rainbows

The formation of a rainbow is a complex matter, inspiring both wonder and curiosity. How they come about took a great deal of time, speculation, and ultimately experimentation.

Aristotle was sure that water droplets were involved, and he knew there was a relationship between rainbow, sun and observer. In his model, however, each water droplet in the air is a tiny mirror that reflects toward the observer a piece of color.

Since each of the mirrors is so small as to be invisible and what we see is the continuous magnitude made up of them all, the reflection necessarily gives us a continuous magnitude made up of one color; each of the mirrors contributing the same color to the whole. We may deduce that since these conditions are realizable there will be an appearance due to reflection whenever the sun and the cloud are related in the way described and we are between them. ... So it is clear that the rainbow is a reflection of sight to the sun. [Meteorologica, Book III, Part 4]

Among his other theories, Robert Grosseteste (c.1175-1235) rejected Aristotle's view that the rainbow was created by reflection; instead, he believed that light passing through clouds, rather than bouncing off them, produced the spectrum. Since every schoolchild knows that refraction breaks white light up into the spectrum, this seems to us like Grosseteste knew what he was talking about.

Then came Roger Bacon a generation later. Some believe he studied under Grosseteste. What is certain is that Bacon knew of Grosseteste's works, because he sometimes quotes them verbatim in his own writing. When it comes to the rainbow, however, Bacon does something that seems baffling on the surface. He rejects the refraction theory and returns to Aristotle's reflection theory. Modern historians shake their heads over this apparent retrograde thinking.

Christ on a rainbow, the Macclesfield Psalter

Bacon had his reasons, however, which make more sense once you know the details of Grossesteste's theory. Grosseteste required three separate refractions to take place, using the borders of the clouds in a complicated lensing effect. Bacon pointed out that a rainbow could appear in a simple spray of water, as in a fountain, and the clouds and interfaces needed for the complex refractions described by Grosseteste were clearly not involved. Bacon also pointed out that the view of the rainbow changed as the observer moved, which meant the rainbow was being reflected toward the observer while keeping its proportions and color. It did not stay "painted on the clouds" as if it were just projected there by light refracted through a cloud lens. (At this point, it is obvious that they did not yet understand "seeing" as light reflecting off objects and into the eye.)

Bacon didn't have all the answers, of course. He struggled to explain the curve in the rainbow, and the fact that it was not a solid half-sphere: why wasn't there color in the center? And he ignored refraction completely when discussing the rainbow, even though he used refraction to explain the occasional halo around the moon.

Did Bacon hold back scientific progress? Hard to say. Grosseteste's theory was valuable in that refraction is crucial in the formation of a rainbow, but he made several assumptions that could not be supported. He ignored the part played in the process by water droplets, even though Aristotle and—more recent to Grosseteste, Albertus Magnus (c.1200-1280)—had insisted on the part they played. Grosseteste thought the entire cloud was the refracting lens. Rainbows were still not properly understood, but the efforts made to comprehend something that could not be touched and experimented on were impressive.*

...and what of the accurate explanation of the rainbow?  A few years after Bacon's death, a disciple of Albertus Magnus would work it out. But that's for another day.

*More on Grosseteste, Bacon and their theories can be found in an article by David C. Lindberg in Isis, Vol.57, #2 (1966).