Spontaneous Generation

In the 6th and 5th centuries BCE, Anaximander looked for an origin of life that did not rely on the gods. He theorized that life arose from the "wet" when acted on by the sun. The way that small life forms appeared in puddles gave him the idea that life—including human life—started as an aquatic form and progressed. This has caused some to claim he was a "prophet" of Darwin and others.

His student, Anaximenes, thought there was a primordial slime consisting of earth and water on which the sun worked to form plants and animals—including human beings.

"Spontaneous Generation" was accepted in the Middle Ages, especially after Aristotle became widely available. His History of Animals explained that animals were generated directly from the elements. Here are some translations of his thinking:

...and of these instances of spontaneous generation some come from putrefying earth or vegetable matter, as is the case with a number of insects, while others are spontaneously generated in the inside of animals out of the secretions of their several organs.

 ...

...all testaceans [creatures having a shell] grow by spontaneous generation in mud, differing from one another according to the differences of the material; oysters growing in slime, and cockles and the other testaceans above mentioned on sandy bottoms;

... 

Other insects ... are generated spontaneously: some out of dew falling on leaves, ordinarily in spring-time...; others grow in decaying mud or dung; others in timber, green or dry; some in the hair of animals; some in the flesh of animals; some in excrements: and some from excrement after it has been voided, and some from excrement yet within the living animal, like the helminthes or intestinal worms. 

(See the illustration, where flies spring from the corpse of a quadruped.)

Some writers actually aver that mullet all grow spontaneously. In this assertion they are mistaken, for the female of the fish is found provided with spawn, and the male with milt. However, there is a species of mullet that grows spontaneously out of mud and sand.

Shakespeare refers to spontaneous generation as if it were still a known and accepted occurrence in the Elizabethan Era. "Your serpent of Egypt is bred now of your mud by the/operation of your sun. So is your crocodile." [Antony and Cleopatra]

Spontaneous Generation was eventually supplanted by the understanding that animals could be extremely tiny (and cause infection, leading to germ theory) and that small eggs or larvae could explain creatures arising from corpses or puddles or slime.

There was one anecdote about the generation of life that required the intervention of a pope to help set people straight. Next time I'll tell you about the barnacle goose myth.

Fastitocalon

Fastitocalon is the name given to a sea creature in an Old English poem called "The Whale."

This time I will with poetic art rehearse, by means of words and wit, a poem about a kind of fish, the great sea-monster which is often unwillingly met, terrible and cruel-hearted to seafarers, yea, to every man; this swimmer of the ocean-streams is known as the asp-turtle.

His appearance is like that of a rough boulder, as if there were tossing by the shore a great ocean-reedbank begirt with sand-dunes, so that seamen imagine they are gazing upon an island, and moor their high-prowed ships with cables to that false land, make fast the ocean-coursers at the sea's end, and, bold of heart, climb up on that island; the vessels stand by the beach, enringed by the flood.

The weary-hearted sailors then encamp, dreaming not of peril.
On the island they start a fire, kindle a mounting flame. The dispirited
heroes, eager for repose, are flushed with joy. Now when the cunning
plotter feels that the seamen are firmly established upon him, and have
settled down to enjoy the weather, the guest of ocean sinks without
warning into the salt wave with his prey (?), and makes for the bottom,
thus whelming ships and men in that abode of death.

Such is the way of demons, the wont of devils:

The poem then shares a moral, comparing the experience of Fastitocalon with the Devil, who entices men with a promise of safety and security before turning and "sinking" them into their own destruction.

The poem continues, explaining another trait of the monster: when it is hungry, it opens its enormous maw, from which a "perfume" emanates that draws a host of fish inside, when it then snaps its jaws shut. This suggests that sailors may have actually seen a whale opening its mouth to feed.

Fastitocalon is the name given to the creature, but that is the Old English version of the original. The poem (and two others) is found in a Bestiary called the Old English Physiologus, part of the Exeter Book. In the Latin version, the creature is called aspidochelone, combining Greek aspis (shield) and chelone (turtle). The Old English version has become more popular (and familiar) thanks to Tolkien writing a poem of that name in The Adventures of Tom Bombadil.

Where did the story of this giant sea-creature-as-island originate? There is a Greek Alexander Romance written in the first few centuries CE that contains a whale-island anecdote in a letter from Alexander to Aristotle. The first voyage of Sinbad (composed c.8th-9th centuries CE) tells a similar tale. Pliny the Elder talks about enormous fish as well. The Babylonian Talmud and Inuit of Greenland folklore both contains legends of a fish so large that it resembled an island and inspired sailors to land on its back. There are many more examples from different parts of the world.

Even St. Brendan encountered it, and gave it a name that has since been used by the Magic: The Gathering card game. I'll share more tomorrow.

Rabies

Rabies, from the Latin rabies which means "madness," has been noticed for a long time. The Codex of Eshnunna (c.1930BCE), found on two cuneiform tablets and pre-dating the Code of Hammurabi, declares the owner of a dog who shows signs of rabies is to be fined if the dog bites someone. Aristotle in 300 BCE described rabies as a disease that can be transmitted from a dog to the dog's victim. Excess salivation was a sign that a dog owner should take care to prevent the dog from biting someone. Rabies was known to Avicenna, who explained its symptoms, method of transmission, and treatment.

Treatment almost always failed until the modern era. There were reported cases of people surviving before modern methods of treatment, but not until Louis Pasteur and Émile Roux developed their vaccine in 1885 was there an effective way to prevent the spread.

But the Middle Ages had a solution: St. Hubert's Key.

St. Hubert, or Hubertus, was the patron saint of hunters and hunting, and therefore of hunting dogs, and therefore of rabid dogs. St. Hubert's Key was an example of a sacramental, which is the church's word for an amulet or talisman. Whereas an amulet or talisman were supposed to have magical properties, a sacramental's effectiveness depended on the faith of the user.

St. Hubert's Key was a piece of iron: either a nail or a cross or cone. They were given out by the monks of the Benedictine abbey where Hubert's remains were, as tokens to go to folk who could not make the pilgrimage to the abbey. These items were hung on the wall of your house for protection against disease.

How did this cure rabies? The piece of iron would be heated and placed on the site of the bite by a priest. The practice is recorded in the 1870s in the Ardennes region (where Hubert was active while alive) of branding a dog with St. Hubert’s Key to guard him from rabies.

Boethius

Boethius (left, with numbers from India)
debating Pythagoras (right, with an abacus)
while Arithmetic looks on

Boethius has been mentioned in passing before for his writing. An early philosopher whose works were very important to the Middle Ages, in life he was an important public servant from a noble family who rose very high before he fell.

Anicius Manlius Severinus Boethius was born about 480 to a prominent family that had produced a couple emperors; his father became a Roman consul in 487 but died shortly thereafter, leaving Boethius to be adopted by the aristocrat and historian Symmachus. Symmachus and Boethius were fluent in Greek, which might have figured into their execution—but we are getting ahead of ourselves.

Boethius went to work for Theodoric the Great, and some of his actions on behalf of the King of the Ostrogoths have survived in the records.

• Procuring or producing a waterclock for Theodoric to give to Gundabad of the Burgundians.
• Finding a lyre player to perform for King Clovis.
• Investigating irregularities in Theodoric's paymaster.

In his famous work De consolatione philosophiæ ["The Consolation of Philosophy"], which he wrote in prison, he says that his greatest accomplishment was getting his sons, Boethius and Symmachus, appointed co-consuls in 522.

Boethius did so well in his career that he was made magister officiorum ["master of duties"], responsible for overseeing all government services. That's probably where the trouble started. Kings and emperors can be mistrustful of those around them with too much power—even if the emperor gave him the power in the first place. Boethius was put in charge of reconciling the differences that had grown up between the Western Roman and Eastern Byzantine Empires. His political powers and education and ability to speak Greek (rare in the West) made him ideally suited for this. He was accused (falsely) of treasonous dealings with the Eastern Emperor Justin I against Theodoric. For this he was exiled, then executed. His adoptive father Symmachus was later put to death on the charge of collusion with Boethius to overthrow Theodoric—a charge which seems unlikely.

He was executed in 525, but his writings survived. He wrote many books, including translations of Aristotle's works on logic; Boethius' translations were the only access to Aristotle's logic available to western Europe until the 12th century. He also produced De arithmetica on the four uses of arithmetic: arithmetic, geometry, music, and astronomy.*

The Consolation of Philosophy is believed to have been written while he was in exile. It covers many topics, one of which gave the modern era the title of one of its most popular game shows. But that's a story for tomorrow.

*These are the four parts of the quadrivium, taught in medieval universities; it is likely that the curriculum was arranged thus because of Boethius.

Peter Damian & Omnipotence

St. Peter Damian, letter writer

Peter Damian (c.1007 - 21 February 1072/3), the author of the Liber Gomorrhianus, was more than just a critic of priests' vices. He was a reformer whose piety caused him to be named a Doctor of the Church and to be placed in one of the highest levels of Heaven by Dante.*

He has a place in philosophy, however, due to one of the 180 letters he wrote. This particular one is called De divina omnipotentia ["Concerning divine omnipotence"]. In it, he discusses two questions that came up in a mealtime conversation during a visit to the Abbey of Monte Cassino.

Before we jump into his answers to the two questions in his letter, we must first bring up the Law on Non-contradiction, which states that a thing cannot be at once true and untrue. Sounds sensible. Aristotle in his Metaphysics states definitively that "contradictory propositions are not true simultaneously." He was building on Plato and Socrates and others.

The two questions that Damian tackles are these:

1. Can God restore a woman's virginity?
2. Can God undo history?

Damian maintains the view of God's omnipotence that says he can restore virginity. Virginity is a good thing, and so regaining it is a good thing; God will do something if it is a good thing. Therefore, God can and would do it, if He felt the situation warranted it. Restoring virginity would require two things: restoring the merit of virginity and restoring the physical change that loss of virginity causes (restoring the "integrity of the flesh"). The first is accomplished by returning to God's Grace, the second a simple matter of God restoring a person's flesh to an earlier condition.

Does this, then, imply that Damian believes that God can undo history? Not quite. In the case of restoring virginity, Damian states that God can do so as a miracle in the present time. He is not undoing an event that took place; He is changing a person's current state back to an original state.

Then what about history?

Damian, after a long and complicated discussion of the law of non-contradiction (and criticism of his peers for not understanding the subtleties of the question), explains that God cannot turn what has been done into something that has not been done. He denies, however, that this is an instance of a lack of omnipotence. Damian argues that God's omnipotence is His ability to bring about what is good. Creating a contradiction by changing what has been done to something that has not been done would be creating a contradiction, and therefore would be a bad thing. It would be turning something into nothing, and God creates things out of nothing, He will not create nothing out of something.

Okay, fine, but what about evil things? Wouldn't it be good for God to undo evil actions? Damian gets a little vague about this, and tells his audience not to worry about evil things. Evil things don't have the same kind of existence/value as good things, and so to erase them does not create a contradiction in the same way as erasing from the historical record a good thing.

Well, who am I to argue?

*In Canto XXI of the Paradiso, in the Seventh Heaven, a bright soul comes to speak to Dante and identifies himself as Peter Damian. The subject of corrupt popes comes up (surprise!).

Stones of Magnesia

A perpetual motion machine powered by magnetism,
described by Peter Peregrinus

Magnets/lodestones have fascinated people for at least 25 centuries. We should first clarify the names. The word "lodestone" was first used in the 16th century and refers to the metal ore with magnetic properties. The word "magnet" was coined by the Greeks far earlier and refers to "stones from Magnesia." Magnesia was a region in Thessaly where it was easy to find the magnetic ore.

Aristotle informs us that Thales of Miletus (625 - c.525 BCE) was certain that magnetism, since it caused the rock to move, was a sign that all things—even rocks—were imbued with divine power; essentially, with "soul." Pliny the Elder mentioned a mountain near the Indus River that was a giant magnet. Superstitions about magnets abounded, and it was incorporated into legends. A mid-twelfth century romance about Aeneas claimed that the walls of Carthage had meanest in them that drew and incapacitated the weapons of Aeneas' men.

Bishop of Paris William of Auvergne in 1231-6 used magnetism as an analogy for the motion of the celestial spheres. A generation later, a French scholar named Peter Peregrinus, or Peter of Maricourt, wrote Epistolæ de Magnete ["Letters on the Magnet"] to a friend, explaining the observable properties of magnets. He describes the two poles, attraction and repulsion, and how to make efficient compasses. His work was so thorough that no one bothered to write another work on magnets until 1600, and that person quoted Peter's work.

Hysteria

from a Latin copy of Gynæcology by Soranus of Ephesus

Hysteria describes two different states: exaggerated or uncontrollable emotion or excitement, and as a psychological disorder in which psychological stress can manifest physical symptoms. The word is derived from the Greek word for uterus, ὑστέρα [hystera]. Hysteria was once assumed to be solely a female medical problem.

It seems to have started with Hippocrates (c.460-c.370 BCE), who maintained that men and women had entirely different bodies: men's humors were hot and dry by nature, women's were wet and cold. Women also had different processes, such as menstruation. Hippocrates did not pass judgment on these differences; they merely needed to be addressed by the practitioner of medicine.

Aristotle (384-322 BCE), however, had other ideas. He postulated that processes like menstruation could be harmful to men, who should avoid women during that time. He also felt men's bodies were perfect and women's were flawed. Women were irrational and unbalanced—literally "unbalanced," because he believed that the uterus "wandered" in the body.

By the time medieval medicine came along, the authority of Aristotle made it clear: over-emotional women were suffering from being unbalanced because of their womb. Hysteria could be treated by removing the source of the unbalance, and the hysterectomy was "born." (Sorry.) Unfortunately, as summarized in this abstract:

The procedure was performed by Soranus of Ephesus 120 years after the birth of Christ, and the many reports of its use in the middle ages were nearly always for the extirpation of an inverted uterus and the patients rarely survived. [source]

The procedure wasn't considered remotely safe until antiseptic techniques began in the 19th century. Even so, it wasn't until the 20th century that diagnoses of hysteria declined, possibly because the general public came to understand that "hysteria" was too easily used as a label for anxiety.

The Rotating Earth

Nicholas Oresme

While re-examining Aristotle, Jean Buridan used observation and brainpower to anticipate some of the ideas we attribute to Galileo and Newton. He carried his ideas further when he put his mind to the question of the Earth's movement.

For most scholars of the Classical and early Medieval eras, the Earth was fixed, and the Heavens rotated around the Earth once each day. Buridan didn't like this: the Heavens are so much larger than the Earth; why would God design such an inelegant system? Moving the Earth would be easier.

Ptolemy knew this could not be, because if the Earth were rotating, there would be a constant rushing of wind as the air of the atmosphere passed over the land underneath it. Buridan scoffed at this: the atmosphere would be rotating just as the land does. There was no reason to dismiss the idea that Earth rotated daily.

For Buridan, however, empirical evidence was crucial. Of course, his predecessors argued, the Earth clearly does not move; we can see that. Buridan, however, likened the situation to being in a boat on a river. An observer on a second boat that was tied to the bank would see the first boat moving, but if the observer on the second boat could not see the surrounding landscape, then he would not know which of the boats were moving. The problem, Buridan knew, was that without an outside frame of reference, one cannot tell if it is the Earth or the Heavens that is moving. He needed an experiment, and he thought of one.

...and that's when he made his mistake.

Here was his idea: shoot an arrow straight up above your head. If it comes back down where you are standing, then the Earth is stationary. If the Earth rotated under it, then the arrow would come down somewhere off to the side.

He didn't realize that the same property that moves the atmosphere along with the ground would carry the arrow along as well. It would be Buridan's most brilliant student, Nicholas Oresme (c.1325-1382), who would realize and state that the arrow moves along with the Earth and atmosphere. Lacking a way to definitively prove his ideas, however, Oresme would ultimately fall back on the Bible for guidance on this issue.

Nominalism vs Realism

Realism [link]

At the foundation of philosophy is a question: what defines reality? There are several questions that are connected to this. Let us start with: when we say that a lot of different animals are all dogs, to what quality are we referring that makes the Dachsund and the Great Dane both dogs? Is there an essential quality of "dog-ness"? Some universal concept that is inclusive of all dogs, despite the particular differences between breeds?

There it is: universals and particulars.

Realism says that both universals and particulars exist. That is, we recognize that different dogs/houses/trees are those things because, although they have different particulars, there is a universal essence of dogs/houses/trees that exists. Plato and Aristotle were Realists.

Nominalism says that the world is made only of particulars. Things we see are put into categories by our thought processes and our language, not by the existence of some abstract universal. William of Ockham and Jean Buridan were Nominalists.

In the two diagrams shown, we see that in Realism, although John and David have different Particulars, they are defined by their Universal quality as human beings. Nominalism, however, shows John and David only defined by their Particulars. The category of Humanity is created by us. There is no abstract "Humanity" essence that exists independent of John and David.

Nominalism [link]

Getting at the truth produced some fascinating thought experiments. One—The Puzzle of Theseus' Ship—was posed by Plutarch (46-120 CE). The ship of Theseus was preserved in Athens for several generations. As pieces of it decayed, they were replaced with new wood, so that the ship would stay intact. If a thing is based on its particulars, then with the particulars of this ship having changed over the years, is it still Theseus' ship? If there is some universal of Theseus' ship (as Realism says) then it is still his ship. If there are only particulars (as Nominalism says) then it isn't.

British philosopher Thomas Hobbes (1588-1679) took this a step further: if all the removed pieces were assembled into a complete ship, then which is Theseus' ship? Are they both Theseus' ship? He concludes that this would be absurd.

Even the early scholars understood that there were problems with these concepts, and struggled to reconcile the issues. Still, they did their best to understand how reality worked, and how that would help them to understand everything else.

...such as whether we have individual souls. That discussion will take us back to Averroes tomorrow.

The Commentator

Statue commemorating Averroes in Córdoba

Averroes (1126-1198) was born in Córdoba into a family of distinguished jurists and scholars at a time when Islamic culture was flourishing in Spain. He probably would have spent his life as a judge if not for his mentor and friend, the physician Abu Bakr ibn Tufayl, who told him that he should write commentaries on the works of Aristotle. The problem seen by ibn Tufayl was that Aristotle was too obscure either because of the ambiguity of his own writing or the shortcomings of his translators.

Averroes, whose real name was ʾAbū al-Walīd Muḥammad bin ʾAḥmad bin Rušd, embraced the task so thoroughly that, to the West, he became known as "The Commentator." His scholarship was embraced across cultures: Jacob Anatoli translated Averroes' Commentaries into Hebrew. Anatoli's colleague and friend Michael Scot translated some directly into Latin.

He analyzed and promoted most of Aristotle (and Plato's Republic) to the known world, as well as writing dozens of books of his own. So far as we know, he did not have access to original texts—there is no evidence that he knew Greek—and so his commentaries are based on Arabic translations of Aristotle.

Unfortunately for him, his rationalist views often got him into trouble when they came up against Islamic theology (which he had studied extensively). He was, in fact, banished by a caliph to whom he had been the personal physician, because some side remarks in Averroes' writing (such as "that Venus is one of the gods") struck the caliph as blasphemous. Fortunately, Averroes was allowed to return home prior to his death.

One of his most radical ideas, based on Aristotle, was that there were multiple intellects, but only one shared soul for all of mankind. To explain that raises more questions, however, unless first we look at a debate I have been putting off for months. Tomorrow, therefore, we will (finally) discuss Nominalism vs. Realism.

Jacob Anatoli

Daily Medieval has frequently mentioned the importance of Arabic texts in the transmission of knowledge to Western Europe. Arabic, however, was not a commonly known language, and Arabs did not have a strong presence in Western Europe. Arabic culture often brushed up against Latin culture in the southern Mediterranean, as mentioned Salerno, or when a scholar such as Michael Scot made it a point to learn Arabic. Scot probably had help in the form of Jacob Anatoli.

Jacob ben Abba Mari ben Simson Anatoli (c.1194-1256) grew up in southern France, and gained such a reputation for scholarship that he was invited to Naples by Frederick II, who gathered several other academics to his court, such as Scot and Fibonacci. Anatoli became known for his translations of Arabic texts into Hebrew, and he very likely aided Michael Scot in his Arabic translations. Roger Bacon explains that Scot was aided by a Jew named Andreas, and some scholars believe "Andreas" to be a misunderstanding of "Anatoli."

Of his non-translations, the greatest work is the Malmad ha-Talmidim (the title is a pun, being interpreted either "Teacher of the Students" or "Goad to the Students"). The Malmad shows a wide range of knowledge, incorporating the Old Testament and Jewish commentators, but also the New Testament, Aristotle, Plato, and Averroes. His egalitarian approach to Christian and Muslim matters was refreshing, but Judaism still had special status; he wrote "the Greeks had chosen wisdom as their pursuit; the Romans, power; and the Jews, religiousness." He tells us that a non-Jew who seeks religious Truth should be respected by Judaism and not mocked.

Anatoli extended this intellectual courtesy to Frederick II, incorporating remarks by the emperor in his works. He also mentions a Christian whom Anatoli considers a second master (after Anatoli's own mentor, Samuel ibn Tibbon); this "master" has been equated to Michael Scot.

As for his Arabic translations, Anatoli's crucial contribution was exposing the West to the work of Averroes, one of two Arab scholars (the other was the medical expert Avicenna) whose work is considered fundamental to the Middle Ages.We'll look at Averroes tomorrow.

Defeating Eternity

How long has the universe existed? Has it been around forever? Did it have a beginning? Could it have a beginning? These questions troubled the ancients.

Aristotle in his Physics tried to answer this through reason. Everything that comes into being does so from something that already exists; matter is made from matter, after all. The matter of the universe would have to come into being from some underlying matter; it couldn't come from nothing. For the matter of the universe to come into being, some matter must have existed before it. This statement is ridiculously self-contradictory, and therefore could not be taken seriously. The universe must have always existed.

Others supported Aristotle. Critolaus (c.200-c.118 BCE) couldn't believe that human beings would ever stop simply procreating into eternity. In the Early Medieval Period, Proclus (412-485) produced De Æternitate Mundi (On the Eternity of the World) with 18 proofs.

This belief was about to collide headlong with Christianity, however. The Bible makes it clear that there was a moment of Creation. That being the case, the universe cannot have been eternal.

John Philoponus (490-570) was a prolific and controversial writer who realized that Aristotle needed to be questioned on some things. Although he would be condemned after his death as heretical for interpreting the Trinity as three gods instead of one God, he was known in his lifetime for defending the Biblical necessity of a universe with a starting point. He wrote "Against Proclus" in which he challenged every one of Proclus' arguments. The basis for his argument is simple, and referred to now as the Traversal of the Infinite. If the existence of something relies on the existence of something else prior to it, then you need to account for the existence of the prior thing. That prior thing would rely on the existence of something before that, and so on. You have to have an infinite series of assumptions that something existed before the thing that came afterward, and never actually explain where any of the substances came from. The world could not possibly be infinite, and must have been created by a divine being.

The Ring of Fire vs. The Flood

15th century portrayal of Ptolemy's map

Prior to the Age of Exploration, human beings in the western hemisphere did not attempt to travel long distances by sea and discover distant lands.* This was partially because ships that could handle a very long voyage were not able to be built or provisioned easily for such a journey.** Another reason is that the world was "known" to be shaped so that long voyages were fruitless.

Eratosthenes (c.276-c.195 BCE) had established in the Classical Era the spherical nature of the Earth through simple and clear experimentation; no one disputed that. (His math on Earth's diameter was probably a little off: the unit of measurement he used probably gave him an Earth 4000 miles larger around than it is.) What was up for debate was the question of what existed "over the horizon."

Aristotle (384-322 BCE), upon whose scholarly shoulders the Middle Ages tried to stand, loved symmetry. It made sense to him that there were five zones (from the Greek word meaning "girdle") around the Earth. The extreme top and bottom were icy cold and uninhabitable. Just inside of them were the temperate zones where humans and animals lived—note: he believed both temperate zones were inhabited. In the middle it was so hot—and clearly, the further south you go from Greece and the Mediterranean the hotter it got—that it was uninhabitable. Pliny (23-79) said that this central zone was so hot that it was actually a ring of fire and was unlivable and impassable, so we would never be able to visit the people living in the southern hemisphere.

Wait, said Christianity. That can't be. The Flood covered the whole world, and when the waters receded, the Ark of Noah came to rest on Mt. Ararat in Turkey, from which all the animals strolled away and repopulated the world. If the ring of fire at the equator is impassable, how can there be animals living beyond it? Worse, if there are people living in the southern temperate region, how are we going to reach them with the Word of God?

Proving that classical scholars did not always agree, Ptolemy presented different problems in geography. His Geography was translated and made available to Western Europe in 1406. His map (depicted above in a 15th century version printed in Ulm) showed that all you had to do was sail far enough south to reach the southern lands in the world, but he also extended the bottom of Africa eastward, enclosing the Indian Ocean. This meant you could not sail to the Indian Ocean and therefore to India, but would forever have to use the Silk Road (and incidentally pay tolls at every border crossing, something sailors get to avoid).

The Age of Exploration changed all this. In 1473, Aristotle was proved wrong with a Portuguese ship exploring the west coast of Africa passed south of the Equator. In 1488, another Portuguese ship sailed around the Cape of Good Hope and reached the Indian Ocean. India and the east were accessible by ship after all, and the Portuguese quickly established those shipping routes.

Ptolemy's Geography was erroneous in another way. He estimated the Earth's circumference at thousands of miles smaller than Eratosthenes. Since no one cared to duplicate Eratosthenes' experiments and determine the distances involved, Ptolemy might have been taken as truth by some. His estimates of the size of a spherical Earth would put Asia thousands of miles closer to Europe by sailing west. With Portugal dominating southern routes to the East, was it Ptolemy's miscalculation that prompted Spain's Columbus to try a bold plan to establish a different and (he thought) shorter route?

*Perhaps some day we'll get to some of the rare cases of accidental discovery of previously unanticipated lands.
**I have been aboard replicas of Columbus' ships; they are frighteningly small considering the journey they made.

Pre-Inertia

Expositio & questiones manuscript

Jean Buridan (c.1300-c.1361) was a University of Paris scholar who was not afraid to tackle some of the big scientific and philosophical issues of the day. That meant, in some cases, taking a critical look at one of the most revered figures in science and philosophy, Aristotle. Buridan, like William of Ockham (c.1288-c.1348),  believed in the observable reality around him, and believed that observation of the world was the key to understanding it. Challenging Aristotle could be risky, but as more and more scholars observed the world around them, they realized that Aristotle's theories needed amendment. He wrote Expositio & questiones (Expoition and questions) to analyze Aristotle's work.

For example, Aristotle believed that an object set in motion—let's say, a rock thrown by a human hand—continues to move after it has left the hand because there must be some continuous external force exerted on it. He theorized that, in the same way a hand swished through water creates little eddies and swirls in the water around it, so the rock's movement is continued by eddies and currents of the air. If there were no movement in the medium that helped carry the rock forward, he believed, the rock would stop its forward course (and presumable drop the the ground). The currents eventually faded, allowing the rock to end its forward flight.

Buridan was not satisfied with this. Building on the work of others (such as John Philoponus and Avicenna, both of whom deserve their own entries some day), he believed that there must be a property in the rock itself that accounts for its action once it has left the motive force of the hand. He called this property of the object impetus (from Latin impetere, literally "to rush toward, to attack").

The property or quality of impetus was clearly changeable. To hurl a heavy rock required you to give it more impetus than to hurl a pebble. Also, impetus was obviously used up over time, allowing the rock to cease its movement and fall. He also explained that a falling object gained impetus the longer it fell (are you paying attention, Galileo?). Unlike Aristotle, who believed that the medium of air in which the object moves helps it along, Buridan saw the air as resistance, causing the object to use up its impetus.

He expanded this theory by looking up. A question had bothered some philosophers for ages: why don't the planets slow down? Will they move forever? Buridan extrapolated his theory to say that a thrown rock in a vacuum would experience no resistance and its impetus would last indefinitely. If the planets were moving in a vacuum...

Well, actually, he couldn't go that far. He agreed with Aristotle that a vacuum couldn't exist in space, since there was no container to keep matter from rushing into the empty area. If above our atmosphere were filled with quintessence, however, Aristotle's "fifth element" that was pure, unchangeable, and frictionless, then the impetus imparted to the planets by whatever initial agency would continue to move forever! The idea of an eternal universe was supportable by science!

Buridan's Ass

Buridan's Ass is the name given to a paradox: that a hungry and thirsty ass placed exactly in the middle between water and hay will be unable to choose because neither choice is preferable or closer; he will therefore die of thirst and hunger. The paradox is named for Jean Buridan (c.1300-c.1361), who studied and taught at the University of Paris. He had a reputation for being a bright and charismatic figure who had a way with the ladies, but that last part might have been spread by his detractors.

But Buridan, who wrote several works including answers to puzzles such as the liar paradox, never discussed the dilemma of the ass; he might have, because it had been around for hundreds of years.

Aristotle mocked the paradox in his De Caelo (On the Heavens). There was an idea circulating that one could explain the unmoving nature of the Earth simply because it was round and centered among all that existed, and therefore all forces acted upon it equally, maintaining an equilibrium. Aristotle mocked this idea by saying it was as ridiculous as if to say that "a man, being just as hungry as thirsty, and placed in between food and drink, must necessarily remain where he is and starve to death." Other early philosophers commented in this dilemma as well.

Why did it get ascribed to Buridan? In his works, he does consider that a rational choice could not be made by a rational person between two equally good options:

Should two courses be judged equal, then the will cannot break the deadlock, all it can do is to suspend judgement until the circumstances change, and the right course of action is clear.

This was just a "thought experiment" for him, however. He did not believe this would in fact lead to total inaction: he believed in a moral determinism that would lead one to a choice, even though that choice or preference might come through an unknowable thought process. Later writers mocked him by laying the burden of the ass paradox on him.

Buridan and Aristotle would cross paths on another issue, however: when a thrown object leaves the hand of the thrower, what keeps it moving? Aristotle had a theory that was clung to by many for centuries. Buridan had a different idea, one that anticipated Newton by about 300 years.

But that's a story for another day.

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.

Got Silk?

Silk was not a medieval invention. According to Chinese tradition, Empress Si-Ling-Chi in 2460 BCE watched silkworms spinning cocoons; she unwound several cocoons, then ran the strands together to make thread, then wove the result into cloth to make a robe for Emperor Huang-Ti.

The Silk Road routes

Unverifiable, but it may very well be true. What is slightly more historically documented is that China guarded the secret of this magnificent fabric for centuries, but was willing to manufacture the cloth and sell it for very high prices to others. Wealthy people from other countries would gladly pay large sums to purchase it—soft and smooth, light to wear, dyed easily—so knowledge of this material spread. India somehow figured out the secret and was manufacturing its own silk by the 2nd century CE.

Ezekiel mentions silk, which means it was known to the Middle East in the 6th century BCE. Aristotle mentions the process of dealing with the cocoons, but the knowledge must have been lost for awhile, because it seems to be a mystery to that part of the world centuries later. We are told that Julius Caesar (100-15 March 44 BCE) had silk curtains. It is thought that the Romans first encountered silk in the hands of the Parthians in the first century BCE. By the end of the 1st century CE, Rome was trading for silk with the Parthians; we don't know what kind of "mark up" the Parthians were putting on the silk that they got from the East, but it was probably substantial. Although more than silk was traded between the East and West, silk was one of the few things only available from the Far East, and so the collection of interconnected trade routes from China and India to Byzantium and Alexandria became known as the "Silk Road."

Of course, it is cheaper to manage production yourself, and the Byzantine scholar Procopius (500-565 CE) tells us how some Nestorian monks* gave the Emperor Justinian the secret: the thread comes from silkworms that could not survive transportation, but their cocoons would travel well if insulated in dung and fed on mulberry leaves when hatched. Byzantium created a thriving silk industry and supplied Europe for centuries. The silk factories were staffed by all-female crews, and so were called gynaecea—after the name given to the section of a Roman or Greek home devoted to women.

Marco Polo on the Silk Road

The cycle of industrial espionage continued, however, when Muslims, who learned the secret of silk when they conquered Persia, took over Sicily and Spain. By the 13th century, Europe was producing its own silk and purchasing less from Byzantium. By the 15th century, France had its own factories. This was necessary, according to Louis XI, because purchasing silk from Italy created a trade deficit for France of 40-50,000,000 gold écus.**

Silk is different from cotton or wool in that it is not spun; rather, two or more strands are twisted together. To produce this, new techniques were invented. The simple reel is said to have been first devised for holding strands of silk, which could be up to a mile long. Two reels would be set up to unwind simultaneously so that their strands could be twisted together in a technique called "throwing."

The Middle Ages loved silk so much that a whole new vocabulary was created to describe its uses in fabrics:

• alexander - a striped silk
• baldachin - a warp of gold thread with a woof of silk
• begin - 14th century rayed silk fabric
• camlet - half silk/half hair (such as angora)
• cendal - woven silk material
• ecarlate - high-quality silk
• gauze - semi-transparent silk (from 13th century onward)
• imperial - silk with gold thread; originally from Byzantium, later called baldachin
• osterni - silk dyed purple
• samite - silk with interwoven gold or silver threads
• sarcenet - thin soft silk with slight sheen; sometimes called "shot"
• tartaire - silk from Tartary

...and in all these centuries, it hasn't lost its luster.

*Remember the Nestorians? They were a branch of Christianity deemed heretical a century before Procopius, who made their home in the East where William Rubruck ran into them.
**Story of the Silk Road by Yiping Zhang, p.146 (I don't normally bog things down with citations—I assume you trust me!—but this number was so ... impressive that I felt the need to point to a source. It may be a huge exaggeration.

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).

Frederick II

Frederick II of Sicily (1194-1250) has crossed the path of this blog more than once, but has not yet been featured.

He declared the Edict of Salerno, separating physicians and pharmacists.
Frederick was interested in math and science, and was friendly to and supportive of Fibonacci.
He promised to go on the Fifth Crusade, mentioned here, but never participated; he was blamed for its failures by Christians all over Europe as well as Pope Honorius III (who had been Frederick's tutor while young).

From the time he was declared Holy Roman Emperor in 1220 until his death 30 years later, he was a tremendous influence on science and culture, but a difficulty for popes and religion—odd, considering he willingly took the title Holy Roman Emperor. Although Pope Innocent III was his guardian growing up, Frederick often said blasphemous things, supposedly mocking Moses and Jesus and Mohammed for being frauds. His public attitude toward religion was unusual for his era and position, and Dante's Inferno places him in the circle of hell reserved for heretics.

He was, however, also possessed of a rationalism that was unusual for his era. He hired Arabs/Muslims as soldiers and personal guards; he hired Jewish scholars to be at his court. He pointed out the unfairness of trials by ordeal, because the stronger man would always win regardless of guilt or innocence. He hired the mathematician and scholar Michael Scot (of whom Honorius III thought very highly) to, among other things, make new translations of Aristotle and Arabian works into Latin. Michael Scot's translation of Aristotle was done with the help of Hermannus Alemannus ("Herman the German").

He had three wives and several mistresses. His third wife was Isabella of England, the daughter of King John Lackland. It was a political marriage, taken on because marrying an English princess would make his political opponents lose support from England. Once Isabella arrived in Sicily, she was sent to live in seclusion in Padua with only two of her English retainers.

Although Frederick had a profound and positive impact on laws and science, his personal manner made him many enemies and detractors. The Hohenstaufen lineage, which had included Frederick Barbarossa, lost power after Frederick II's death.