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Natural Science - Year I

Unit 21: Medieval Cosmology

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History Weblecture for Unit 21


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History Lecture for Unit 21 History: Medieval Cosmology

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Lecture outline:

Medieval Cosmology: Reconciling Aristotle and Christianity

For most philosophers in Western Europe in the ninth and tenth centuries (there were a few!), knowledge of the previous work done by the Babylonians, Egyptians, Greeks, Romans, and Arab thinkers was limited to references in Augustine and the other church fathers, most of whom cited Plato or his followers, and a few scattered encyclopedia-type works, such as the De Nuptiis Philologiae et Mercurii et de septem Artibus liberalibus libri novem ("On the wedding of Philology and Mercury and of the Seven Liberal Arts") by Martianus Capella and the Etymologiae ("Etymologies or origins of words") by Isidore. In the ninth century, however, Charlegmagne fostered a renewed interest in learning.

The Translators

By the tenth century, exposure to Middle Eastern countries through trade and the Crusades began to expand the horizons of Western Europeans to include both new and old sources of natural philosophy. Gerbert was one of the tenth century teachers to benefit from an education in Spain, where he read works long lost to the Latin West, including the quadrivium texts of Boethius, Aristotle's logical works, and a number of mathematical treatises. Later as lecturer at Reims in France and as Pope Sylvester II, Gerbert promoted a reawakening of interest in classical ideas.

Many found the logical works of Aristotle especially appealing. Anselm of Canterbury attempted to push the limits of philosophical method to determine whether fundamental doctrines of Christianity could be judged true by logical criteria, an effort for which he became known as "the father of Scholasticism". He authored what became known as the "ontological proof of God's existence", and set the stage for a new debate on the relationship of reason and revelation in determining divine truths. Peter Abelard, who taught at Paris in the mid-twelfth century, was inspired to collect and systematically examine conflicting opinions of the church fathers on a series of theological questions. His attempts at a new kind of logical discourse provided the groundwork for what became known as the Scholastic Method.

The twelfth century renaissance was further fueled by the recovery of many works through translations from the Arabic copies and commentaries into Latin. Gerard of Cremona is credited with traveling to Toledo, Spain, to establish a school dedicated to translations; in all, he and his companions put nearly seventy works into Latin, including Euclid's Elements, Aristotle's Physics and De Caelo (on the Heavens), and Avicenna and Galen's medical works.

Chartres Cathedral

At Chartres, outside of Paris, a new type of educational training developed under the leadership of Bishop Fulbert in the early eleventh century, and spread quickly to other schools in France. At the cathedral schools, sons of the local nobility and some of the better-off tradesmen were able to learn to read and write by studying the arts of the trivium: grammar, or basic vocabulary and the rules of writing correctly (in Latin, of course); dialectic, which we call logic; and rhetoric, or persuasion. The students were also exposed to the basic ideas of the four sciences of the quadrivium: arithmetic, geometry, music, and astronomy.

The Universities

With so many new works available, people demanded opportunities where the translations could be heard, and where teachers could be found to explain them, and guide students in maintaining a proper balance between reason and faith. In Italy, at Bologna, Salerno, Naples, Padua, and Pisa, schools concentrating on medicine and medical astrology became popular and profitable centers of learning. At Paris, a school specializing in theology sprang up, followed by establishments at Toulouse, Angers, Orleans, Montpellier, and Avignon, and in England at Oxford and Cambridge. Some of these schools received royal or papal authority to grant universally-recognized degrees to those students who had mastered their coursework in "the arts" or become teachers professing knowledge of medicine, canon and civil law. These universities often started as simple examining boards but eventually drew in scholars to teach, set fees, and became the legal representative of the groups of scholars (collegia) seeking everything from a teacher to teach and a place to gather to decent rental fees from the city landlords.

Paris Latin Quarter

By the end of the thirteenth century, the curriculum for the Master of Arts degree had become more or less standardized throughout Europe. Anyone professing to be properly educated would have heard the logical works and some of the scientific works of Aristotle read, along with the teacher's commentary. He would also have heard the De Sphaera, a summary of astronomy written by John of Holywood, or Sacrobosco in Latin, and at some colleges, he would have had access to the Almagest of Ptolemy, or at least a summary of it called the Theorica Planetarum, the theory of the planets. Many were able to read or hear the ideas of pseudo-Dionysius, which described how the different spheres of the planets were governed by angelic powers of different ranks.

    Sacrobosco's treatment of the movement of the planets inspired a new way of delivering information: the volvelle. Paper circles, triangles, and rulers were fastened to pages in the book in such a way that the reader could manipulate models of the heavens to better understand and even calculate future positions of planets. Take a look at Robert Sabuda's volvelle collection. Be patient! The site has a lot of pictures and make take some time to load.

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    • How would manipulating drawings like these help a reader understand the organization of the heavens?
    • Take a look at the paper astrolabe models. Could such a paper model teach someone how to use the more sophisticated and expensive real instruments?

The Great Synthesis

The result was a mix of ideas about the physical nature of the planets, how to calculate their motions using epicycles and eccentrics, and how to determine their spiritual and astrological influence, at least for the widely accepted (even by the church authorities) purpose of determining medical care. Teachers such as the Dominican professor of theology at Paris, Albertus Magnus, the "great doctor", justified the study of Greek and Arabic learning as a valid source of information on nature. He formulated the principle Experimentum solum certificat in talibus, "experiment alone provides certainty in these matters." In his commentary on Aristotle's de Caelo et Mundo, Albertus determined the purpose of science:

"In studying nature we have not to inquire how God the Creator may, as He freely wills, use His creatures to work miracles and thereby show forth His power: we have rather to inquire what Nature with its immanent causes can naturally bring to pass. (translation from the Catholic Encyclopaedia)"

Albertus followed Aristotle in declaring that mathematics dealt only with abstractions and therefore was subordinate to the realities upon which it drew. Therefore the study of mathematics was simpler and proceeded the study of natural philosophy or physical objects, and both were required in any rigorous preparation for the queen of sciences, theology. Albert's attitude informed the mind of his most outstanding pupil, Thomas Aquinas.

Aquinas attempted to reconcile the world view of Aristotle with his understanding of Christianity, and put much of his thought into the Summa Theologica, which tackles questions of the nature of God, Creation, the Angels, Matter, itself, and man. In his discussion of Creation, Aquinas raises the question of how God could create diversity if He is always One.

    In his discussion of Creation, Aquinas raises the question of how God could create diversity if He is always One. Please read Summa Theologica I, Question 47, Article 1

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    • This is a classical scholastic argument, which always begins with a question.
    • The first part includes reasons (objections) in support of a particular position, drawing on rational explanation, and often on popular interpretations of various authorities.
    • Beginning "On the contrary", the argument takes the real position that will now be defended. The author summarizes the correct position, starting with an historical survey of Greek and Arab authorities. Because he has read Aristotle's Physics, Aquinas is well aware of the theories of the Ionian philosophers. He has also read the works of the Arab philosopher Avicenna.
    • The argument concludes by demolishing each original objection with a response showing why it is wrong.

Aquinas divided knowledge into natural, mathematical, and divine parts in his commentary on Boethius' De Trinitate. Mathematics is based on logical extensions of abstract definitions. Natural science is based on the observations of individuals and knowledge of the physical world comes through the senses. Divine or sacred knowledge comes through revelation. In this way, Thomas breaks with the earlier medieval tradition drawn from the Platonists and Pythagoreans, in which the physical world was itself mathematical. This division between mathematics and natural philosophy (what we might now call at least in part, physics) was to have serious consequences during the Renaissance.

Aquinas' work influenced many people who followed him, not only in theology, but in the sciences and literature as well. One of the more popular writers and near contemporaries of Aquinas was Dante Alighieri, whose Divine Comedy sets Dante on a journey through hell, purgatory, and finally the ten circles of heaven. These are arranged concentrically around the earth, and lead from an earthly paradise at the Antipodes through the spheres of the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, then the sphere of the fixed stars and the Primum Mobile to the Empyrean, or uttermost heaven. Dante places Aquinas among the wise religious men and teachers in the circle of the the Sun.

    Study Dante and the Three Kingdoms of Domenico di Michelino, whose vision of Dante's Hell, Purgatory, and Heaven reflects the concentric-sphere model proposed by Aristotle.

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    • Notice the lower circles in the painting detail near the top of the diagram. There are eight of them; the lowest one is the circle of the moon (directly above the top of the Purgatory mountain).

Occam's Razor

Medieval philosophers were not only challenged by what to include in their divisio scientiarum, but also by what criteria they should use to determine whether one explanation was better than another when both seemed to explain all of the related phenomena. In the fourteenth century, and English Franciscan friar named William of Ockham (also spelled Occam) expressed the "law of parsimony" or law of succinctness. For those of you who are studying Latin, he wrote:

entia non sunt multiplicanda praeter necessitatem

which, roughly translated, means you shouldn't make up more explanation than is absolutely necessary. In other words, if you have two theories that can both explain a set of phenomena,the simplest explanation is the best. This perception that nature could be explained by elegant, simple laws became a fundamental method for selecting theories, or even driving scientists to work on new theories because they felt the existing explanation was too complicated. Here we have an example of theory adoption which does not depend on the actual ability of the theory to describe all the phenomena adequately, but on the form of the theory itself.

Study/Discussion Questions:

Further Study/On Your Own