Roger Bacon's "Opus Majus"

Roger Bacon was born about 1219 into a wealthy family in England. He attended classes at Oxford University, where he learned a love of science from masters such as Robert Grosseteste and Adam Marsh. About 1240 he joined the Franciscans, which might have stifled his interests. There was a prohibition on the order against publishing without special permission from the superiors. This was in place because of a work published previously that was considered heretical.

Bacon looked for support and patronage from the papal legate to England, telling him that educational reform was needed. This was one Gui Foucois, although in England he was known as Cardinal Guy de Foulques. The cardinal was not interested in providing financial aid, but was interested in his work and ideas. Unfortunately, without money, Bacon could not afford the writing materials and scientific equipment to produce what he wanted to send.

Then, in 1265, the situation changed. Guy de Foulques was elected Pope Clement IV. Another request to the new pope returned the same result: Clement wanted the information, but would not send money. Bacon could only assemble a shorter work than he wanted to. The result was the Opus Majus or Opus Maius (Latin: "Greater Work"). Its seven sections (which included some of his earlier writings along with new materials) are:

•The Four General Causes of Human Ignorance (believing in an unreliable source,  sticking to custom, ignorance shared by others, pretending to knowledge)
•The Affinity of Philosophy with Theology (concludes that Holy Scripture is the foundation of all sciences)
•On the Usefulness of Grammar (a study of Latin, Greek, Hebrew, Arabic)
•The Usefulness of Mathematics in Physics (in this section he proposes changes to fix the Julian calendar)
•On the Science of Perspective (the anatomy of the eye and brain; light, vision, reflection and refraction, etc.)
•On Experimental Knowledge (a review of alchemy, gunpowder, and hypothesizes microscopes, telescopes, eyeglasses, machines that fly, and ships driven be steam)
•A Philosophy of Morality (philosophy and ethics)

It was sent to Clement in late 1267 or early 1268; however, Clement died in 1268. We do not know if he even had opportunity to read what he had requested.

"The Science of Perspective" was about optics. In that section, he discussed the anatomy of the eye, and how light is affected by distance, reflection and refraction. He also goes into mirrors and lenses. Most of this knowledge of optics came from Alhazen's Book of Optics, previously discussed here, and Robert Grosseteste's work on optics based on Al-Kindi, of whom I have never written before; I think there's my next topic.

For more on Bacon, use the search feature in the blog.

Asking Questions

Image from Adelard's translation
of Euclid's Elements of Geometry

Being inquisitive is the first step to learning.* In the early Middle Ages, the presence of many classical authorities circulating in Latin, such as Aristotle and Plato, eliminated the need for inquiry in the opinions of many.

The 12th century saw an influx of more works, many of them Greek writings (preserved by Arabs) or Arab writings. The widening of philosophical and scientific horizons by this wave of knowledge caused many scholars to re-think what had been established.

Adelard of Bath (c.1080-c.1152) was an English philosopher who was in a position to translate into Latin for the first time many of the Greek and Arabic works becoming available to the West. After studying at Tours and teaching at Laon in France, he traveled for seven years through Italy, Sicily, Syria and Palestine. He translated Al-Kwarizmi's astronomical tables and Euclid's Elements of Geometry from Arabic, wrote works on the abacus and on his love of philosophy, and a book called Questiones Naturales (Natural Questions) in which he tackled, in dialogue form, 76 questions about the world. One of his themes is the choice of using reason rather than merely accepting authority.

For what should we call authority but a halter? Indeed, just as brute animals are led about by a halter wherever you please, and are not told where or why, but see the rope by which they are held and follow it alone, thus the authority of writers leads many of you, caught and bound by animal-like credulity, into danger. Whence some men, usurping the name of authority for themselves, have employed great license in writing, to such an extent that they do not hesitate to present the false as true to such animal-like men. [...] For they do not understand that reason has been given to each person so that he might discern the true from the false. [Questiones Naturales, VI]

To be clear: Adelard's science is not ideal: his periodic table of elements contains only four substances, which are mixed in various proportions to create all materials. Some animals see better by day or night because of either white or dark humor in their eyes. We see because an extremely light substance (Plato's "fiery force") is created in the brain, gets out of the brain through the two eyes, swiftly reaches an object and learns and retains its shape, then returns to the brain through our eyes so that we "see" what is in front of us. A mirror, whose surface is smooth, bounces back the fiery force, which on returning to us picks up our image on its way and allows us to see our reflection.

Still, his works were copied and distributed, and influenced much of what was to come. His assertion of reason over blind acceptance of classical authorities was an important milestone in scientific thought. Many of his ideas are seen again in the writings of Robert Grosseteste, Roger Bacon, and Hugh of St. Victor. Once the printing press was perfected, Adelard's translation of Euclid became a standard text for a hundred years.


*One of the followers of this blog is part of a group trying to promote inquiry-based learning in young people. Visit Prove Your World to learn more.

Figuring out the Sun

[DailyMedieval is on semi-hiatus for the holidays, and I am re-cycling some older posts. For Christmas I received A Short History of Nearly Everything by Bill Bryson. I have just read the section on the brilliant Lord Kelvin, who estimated the age of the Earth at as high as 400 million years. Interestingly, he kept revising his estimate, from 400 million to 100 million to 50 million and, finally, to 24 million. The difficulty in adhering to his longer estimates, for him and others in the burgeoning field of geology, was not that they could not imagine the Earth being older, but that for the Earth to be that old, the Sun would have to be around—and their best estimates of how the Sun worked could not imagine the nuclear forces that would allow it to produce heat continuously for hundreds of millions of years. This reminded me of the post for 10 June 2012.]

How Does the Sun Work?

Robert Grosseteste (c.1175-1235) is considered by some to be the founder of modern English intellectualism. Among other topics, he focused (pun intended) on light. One of his works sought to explain how the sun produced heat.

He first explained the three methods of heat generation:

1. An object that is hot
2. Motion/Friction
3. The scattering of rays

He determined that Method 1 cannot apply here. For heat to transfer from a hot object, there must be a medium through which it travels, and that medium will heat up during the transfer of heat. Clearly everything between the sun and us does not heat up.

He decided that Method 2 was also insufficient to explain the heat, because the motion that creates heat is caused by two substances moving in opposite directions—for instance, rubbing your hands together to warm them up—and the sun's circular motion does not act upon a second substance moving in an opposite direction: everything up there moved from east to west.

Method 3, he decided, must pertain. He reminds his reader that Euclid explained how a concave mirror can focus the sun's rays to cause a fire. He stated that the sun's rays falling upon the earth are scattered, but reflection by a mirror or refraction by a (clear) spherical body can change the direction of the rays, focusing them via the medium of the dense air and generating heat. For him, this had much to do with the denseness of the medium: he stated that the same amount of light falls on a mountaintop and scattering can be observed there, but the thinness of the medium of air disallows the generation of heat.

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.

Robert Grosseteste

Robert Grosseteste (c.1170-1253) has been mentioned in several posts. His early life, beyond having been born into humble beginnings in Stowe, is unknown. One of our first notes about him is by Gerald of Wales (mentioned here), who recommended him in 1192 for a position in the household of the bishop of Hereford, William de Vere, because of Grosseteste's ability in liberal arts, canon law, and some medicine. He remained in de Vere's household until de Vere's death in 1198, after which Grosseteste drops out of the historical record almost completely.

We are sure he is the Robert Grosseteste who was appointed to the diocese of Lincoln in 1225 and concurrently as archdeacon of Leicester in 1229. The double-duties apparently made him ill within a few years, and he pared down to the position of canon in Lincoln Cathedral, and started lecturing in theology at Oxford on the side. According to Thomas of Eccleston, Franciscan chronicler for the years 1224-1258, Grosseteste joined the Franciscan school at Oxford around 1230.

Association with Oxford and reduced ecclesiastical responsibilities allowed him time for scientific theorizing and writing.

He began producing texts on the liberal arts, and mainly on astronomy and cosmology. His most famous scientific text, De luce (Concerning Light), argued that light was the basis of all matter, and his account of creation devotes a great deal of space to [...] God’s command, ‘Let there be light.’ Light also played a significant role [in] his epistemology, as he followed the teachings of St. Augustine that the human intellect comes to know truth through illumination by divine light. Grosseteste’s interest in the natural world was further developed by his study of geometry, and he is one of the first western thinkers to argue that natural phenomenon can be described mathematically. [source]

From De Sphera, on astronomy

For all his scientific interest, however, his first intellectual love was theology and the direction of the church. He clashed with the papacy several times, leading later scholars to try to label him an early Protestant. But correction is not insurrection (even though his influence can be seen in the writings of a true proto-Protestant, John Wycliffe). Now he is considered a valuable insight into the theology of his time, not a rebel.

There are 120 works attributed with confidence to him. They have not all been translated and examined yet. Focus has been on his theological and philosophical works, but many writings still exist only in manuscript form. His still-unedited scientific works may reinforce the current belief that he proves that pre-Renaissance scientific progress was further advanced than previously thought.

He died on 8 October, 1253, and was buried in a memorial chapel in Lincoln Cathedral.

Postscript: If you are curious about his Latin texts, seek
here.

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).

Fireworks

In honor of Independence Day in the USA...

Everyone knows that to discuss the history of fireworks means talking about China and Marco Polo (1254-1324), but the real history of fireworks in the European Middle Ages may start with Roger Bacon (1214-1294).

Bacon was a Franciscan Friar who spent time at Oxford and may have studied under Robert Grossteste. He has been called the first user of the scientific method, but more careful study of his works suggests that his conclusions and theories were the result of "thought experiments" like many other scholars, instead of actual scientific experimentation. Although Oxford's fairly careful and complete records of degrees given do not show that Bacon ever earned a doctorate, he was nicknamed Doctor Mirabilis (wonderful doctor) for his ideas.

Many volumes have been filled about Bacon, his ideas and discoveries, but today we are interested in gunpowder. At the request of Pope Clement IV, Bacon wrote his seven-part Opus Maius (Greater Work) which discussed (among other things) his thoughts on philosophy, theology, and certain scientific experiments. We know that a contemporary and fellow Franciscan, William Rubruck (c.1220-c.1293), visited the Mongols and witnessed the use of gunpowder in the form of firecrackers. Perhaps Rubruck brought some back. The relevant passage in the Opus Maius is:

We have an example of these things (that act on the senses) in that children's toy which is made in many [diverse] parts of the world; i.e. a device no bigger than one's thumb. From the violence of that salt called saltpetre [together with sulphur and willow charcoal, combined into a powder] so horrible a sound is made by the bursting of a thing so small, no more than a bit of parchment [containing it], that we find [the ear assaulted by a noise] exceeding the roar of strong thunder, and a flash brighter than the most brilliant lightning.

The "no more than a bit of parchment containing it" reminds me of these. He speaks of this again in his Opus Tertium (the Third Work; and yes, there had been an intermediate Opus Minus, the Lesser Work):

Then wonders can be done by explosive substances. There is one used for amusement in various parts of the world made of powder of saltpeter and sulphur and charcoal of hazelwood. For when a roll of parchment about the size of a finger is filled with this powder, it produces a startling noise and flash. If a large instrument were used, the noise and flash would be unbearable; if the instrument were made from solid material, the violence would be much greater.

These are the earliest references in the English-speaking world to gunpowder and fireworks. Whether Bacon ever made his own gunpowder is unknown, however. Some articles will tell you that he could, and encrypted the knowledge in order to prevent its misuse. Claims that Bacon hid the formula for gunpowder in his works cannot be substantiated, however. He seems to know what goes into the formula, but not necessarily in what proportion.  The secret numbers that some modern manuscript detectives claim to have found in his writings produce the wrong ratio for gunpowder to do more than smoke.

Enjoy your day.

Tide Goes In, Tide Goes Out

The Classical World and the Middle Ages wrestled with the cause of the tides for centuries. Although one early scholar (Alpetragius, who flourished in the late 1100s) felt it was caused by some general motion of the world/celestial spheres that ran from east to west, most others (such as Bede and Gerald of Wales) felt it had a stronger connection to the movement of the Moon.
Alpetragius died in 1204, and his theory on the motion that caused the tides was translated into Latin by Michael Scot. This brought it to the attention of Robert Grosseteste (c.1175-1235), who had an explanation for the tides that relied on his theories of light. (The following is from the Questio de fluxu et refluxu maris, attributed to Grosseteste, although that attribution is disputed.)

Remember that there was no working theory of gravity yet; just a feeling that substances could be heavier or lighter depending upon their composition and gravitate (see? in this enlightened age, the concept of gravity pervades even our language) toward like substances: solids fall to earth; liquid (containing more of the element of water) flows to a lower spot to find its kind; fire yearns upward through air, because fire is even "lighter" than air.

For Grosseteste, light imparted force. Rays of light could carry with them the power to generate heat, for instance (see his theory on the sun). He postulated that, when the Moon rose above the horizon, its rays impressed against the waters and pushed them ahead of it, toward the west. This was not as simple and direct as a physical object pushing against water, and so water didn't rush to the shore as soon as the Moon rose. The rays of the Moon started pushing against the sea closest to it, pushing that water toward the observer. When the Moon was overhead, its rays had pushed as much water as it could at that time. Once the Moon passed the zenith and was over land, then the waters started to recede. The Moon then passes west and under the earth, at that point causing (somehow) the tides again.

Grosseteste admits that we don't know everything about this process, and my summary is a radical simplification of his detailed analysis. He notes the changes in tides as the Moon changes its declination, and theorizes that the Sun also "helps" the Moon in some manner.

For more detail, find the Question on the flow and re-flow of the sea (available in Isis, Vol. 57, No. 4 (Winter, 1966), pp. 455-474 in an article by Richard C. Dales) and enjoy.

How Does the Sun Work?

Robert Grosseteste (c.1175-1235) is considered by some to be the founder of modern English intellectualism. Among other topics, he focused (pun intended) on light. One of his works seeks to explain how the sun produces heat.

He first explains the three methods of heat generation:

1. An object that is hot
2. Motion/Friction
3. The scattering of rays

He determines that Method 1 cannot apply here. For heat to transfer from a hot object, there must be a medium through which it travels, and that medium will heat up during the transfer of heat. Clearly everything between the sun and us does not heat up.

He decided that Method 2 is also insufficient to explain the heat, because the motion that creates heat is caused by two substances moving in opposite directions—for instance, rubbing your hands together to warm them up—and the sun's circular motion does not act upon a second substance moving in an opposite direction: everything up there moves from east to west.

Method 3, he decides, must pertain. He reminds his reader that Euclid explains how a concave mirror can focus the sun's rays to cause a fire. He states that the sun's rays falling upon the earth are scattered, but reflection by a mirror or refraction by a (clear) spherical body can change the direction of the rays, focusing them via the medium of the dense air and generating heat. For him, this has much to do with the denseness of the medium: he tells us that the same amount of light falls on a mountaintop and scattering can be observed there, but the thinness of the medium of air disallows the generation of heat.