X. THE RECOVERY & ASSIMILATION OF GREEK & ISLAMIC SCIENCE

The New Learning

The educational revival after 1000 a.d. started with a revival of classical (Greek & Roman) knowledge.

This revival grew stronger in the 12 & 13^th centuries.

The 'new' ideas posed challenges for how to integrate them into existing theological beliefs -- particularly the more philosophical works.

Aristotle in the University Curriculum

Aristotle's influence in the schools grows after 1200, partly through the commentaries of the Muslim philosopher Avicenna.

Problem in Paris: church finds some of Aristotle's work dangerous (there are accusations of pantheism). Pope Gregory appoints a commission to purge the objectionable parts. But the commission doesn't seem to have done it.

The influence of the ban wears off in a few decades, and in 1255, Aristotle becomes a mandatory part of the curriculum in Paris. Aristotle is taking over.

Points of Conflict (between Aristotle & Christianity)

Aristotle says the universe is eternal (in the past direction).

Contradicts Christian doctrine of creation.

Aristotle has objects acting according to fixed natures. Aristotle has a 'Prime Mover' (a being that moves other things but is not itself moved; the ultimate cause of all motion); however, the Prime Mover is unchanging and its effects are regular & predictable. Prime Mover is also impersonal; doesn't care about human affairs.

Contradicts concept of miracles.

May contradict concept of a personal God who loves & helps individual humans.

Aristotle has some astrological beliefs (the stars influence human affairs)

May conflict with doctrine of free will.

Aristotle's 'soul' is simply the form of the body.

Contradicts immortality of the soul.

Averroes developed a concept of an immortal soul; however, it was a sort of collective soul (there is one shared by all humans).

Again, contradicts Christian notion of personal immorality (you will survive as an individual, into the afterlife).

These conflicts seem to reflect a more fundamental one: The rationalistic and naturalistic tendencies of Aristotle, as contrasted with the church.

Some theologians worry that Aristotle is supplanting Christianity.

Resolution: Science as Handmaiden

Aristotle's influence proved irresistible, basically because he was such a great philosopher. His writings provided a comprehensive understanding of the natural world, and reality in general. (He wrote about physics, metaphysics, ethics, biology, perception, logic, aesthetics, & cosmology.)

Grosseteste: commented on Aristotle & tried to combine Aristotelian doctrines with neoplatonism.

Roger Bacon: Tried to convince the church that Aristotle was useful for theology. Theology is the queen of the sciences.

St. Bonaventure: basically agrees w/ Bacon, but is more cautious.

Thinks Aristotle is just wrong on the points of conflict listed above, because Aristotle didn't have the benefit of divine illumination.

Held that God was active in every case of cause & effect in the natural world. (The cause produces the effect only because God wills it.)

[ Side note: 2 mendicant orders at this time: Franciscans (founded by St. Francis) & Dominicans (founded by St. Dominic). Took vows of poverty. Bonaventure became head of the Franciscans. Albert & Aquinas were Dominicans.]

Albert the Great (St. Albertus Magnus, patron saint of natural scientists), 1200's: taught in Cologne & Paris.

Composed a comprehensive interpretation of the Aristotelian corpus. Basically accepted Aristotle, but corrected Aristotle periodically on the basis of his own observations. Wrote over 8000 pages on Aristotle.

Rejected the eternity of the universe as philosophically absurd.

Rejected doctrine of soul as form of the body.

Took a quasi-naturalistic approach: although God ultimately causes everything, God normally works through natural mechanisms, and we should try to understand these.

Did not think that philosophy and theology could conflict, if carried out properly.

Thomas Aquinas (St. Thomas): Student of Albertus Magnus. Called a 'dumb ox' by fellow students.

Natural reason & revelation are both legitimate means of knowledge, and they do not conflict. Both are given by God.

Philosophy can assist theology by (a) proving some basic propositions of the faith, (b) answering objections to the faith.

Famous book: Summa Theologica. Comprehensive theological treatise, defending Christian doctrine against various objections. [Takes the form of a question, followed by arguments against the Christian doctrine, followed by quotations from some authority (usually the Bible), followed by arguments defending the theological item in question, followed by answers to the objections.]

Synthesized Aristotle w/ Christianity. Philosophy of "Thomism" later became the official philosophy of the Catholic church.

[ Aquinas claimed 5 proofs for the existence of God. They were based on (a) motion, (b) efficient causes, (c) necessity & contingency, (d) gradations of goodness, (e) teleology in nature.]

Radical Aristotelianism and the Condemnations of 1270 and 1277

A few radical philosophers depart from Thomas & Albert, notably Siger:

Maintains that philosophy can come into conflict w/ theology. Argues that reason leads to the doctrine of the eternity of the world.

Professes to side with faith in such conflicts, but he may have been lying to placate the church.

In 1270, the bishop of Paris issues condemnations of 13 propositions allegedly taught by Siger.

In 1277, he issues a longer list, including 219 propositions, the teaching of which is grounds for excommunication. They include:

Eternity of the world

Monopsychism

Denial of personal immortality

Denial of free will

Various propositions about things God couldn't do, such as creating multiple universes, moving the celestial sphere, or making an accident w/o a subject. (B/c Aristotle showed these things to be impossible.)

The significance of this: a reactionary, anti-Aristotelian move.

The Relations of Philosophy and Theology after 1277

No one aimed to completely remove Aristotle, but only to discipline Aristotelian philosophy.

Aristotle's influence continued to grow, and Thomas was made a saint in 1323.

More about divine omnipotence. Historians have disputed whether the effect of this doctrine was

a) To impede natural science, because the universe need not be governed by predictable laws, since God could do anything he likes. Or

b) To promote natural science, because in order to find out which world God actually did create, one would have to do empirical observation.

Neither of these seems quite right.

1. Web page of William Lane Craig, contemporary defender of the Cosmological Argument:

http://www.leaderu.com/truth/3truth11.html

2. Bertrand Russell's famous essay, "Why I Am Not a Christian":

http://www.geocities.com/Athens/Delphi/2795/whynot.htm

1. Could God make a stone so heavy he couldn't lift it?

2. How can God be 'all-powerful', since he is incapable of being corrupted, or doing evil? (Anselm discusses this question.)

3. Conflict between divine omniscience & human free will. If God knows what you are going to do before you do it, are you still free not to do it?

4. The problem of evil: a) If God is omniscient, then he is aware of evil; b) if he is all-powerful, he is able to remove it; c) if he is all-good, then he is willing to remove it. But if God is aware of evil, and both willing and able to remove it, then how does evil exist?

The Structure of the Cosmos

Early medievals accepted Platonic cosmology (based on Plato's Timaeus).

Later, Aristotelian cosmology supplanted Plato's, in the areas where they differed. Ex.:

Plato had all the physical world composed of the same kind of stuff (the 4 elements).

Aristotle had the celestial (superlunar) realm composed of a different sort of stuff, 'ether' (a.k.a. 'quintessence').

Aristotle's system of planetary spheres.

More elements of medieval cosmology:

The cosmos is a large but finite sphere

Earth is at the center

The cosmos was created (not eternal).

The Heavens

What is outside the celestial sphere?

According to Aristotle, (a) there is no void space, but (b) the cosmos is a finite sphere. It follows that (c) space is a finite sphere.

Medievals rejected this for two sorts of reason:

a) A religious reason: In the condemnation of 1277, it was said that God could move the cosmos. It seems to follow that there is a space to move it into, and further, that a void space could exist, since a void would be left behind by the cosmos' motion.

b) Anyway, what would happen if you got to the edge of space and then you stuck your hand out?

Where is the celestial sphere?

According to Aristotle, location is a relationship of a thing to its container. As a result, the celestial sphere has no location (nor does the universe as a whole).

Many medievals found this unbelievable. One solution is to redefine location as a relation to the thing contained, rather than the container.

Problem: the Bible makes a distinction between the heavens and the firmament, but this doesn't fit w/ Aristotelian cosmology. [Gen. 1:1: "In the beginning God created the heavens and the earth." Genesis 1:6-7: "And God said, 'Let there be an expanse between the waters to separate water from water.' So God made the expanse and separated the water under the expanse from the water above it."]

Some postulated additional spheres, above the planetary spheres (but before the fixed stars), including a sphere of water, but possibly not the same kind of 'water' we have on earth.

Nature of the spheres:

Early thinkers thought of them as composed of fire.

Later, under the influence of Aristotle, people thought of them as 'aether'.

They fit together perfectly (remember: no void space) and rotate without friction between them.

Unmoved movers:

Acc. to Aristotle, there was an 'Unmoved Mover' for each of the planetary spheres. (Remember that all motion requires a cause.)

The 'Prime Mover', the unmoved mover for the celestial sphere, was identified with God by the medievals.

Q: What about the other unmoved movers? Some identified them with angels. Others denied the need for such additional unmoved movers.

What about Ptolemaic epicycles?

Some medievals made the spheres thick enough to contain the planets on their epicycles. (Derived from the Muslim astronomer Alhazen's suggestion.)

This, given how the spheres are tightly packed, enabled calculations as to the diameter of the heavens.

Result: The celestial sphere is 73 million miles in radius. This figure survived until Copernicus' revision in the 16^th c.

The Terrestrial Region

A form of geographical knowledge: the 'periplus':

A list of major landmarks encountered as one travels along a coastline. Pliny & St. Isidore provided them for the European & African coastlines.

Division of the earth into climes:

Frigid zones (arctic & antarctic)

Temperate zones, northern & southern.

Europeans & all known peoples live in the northern temperate zone.

The existence of people in the southern temperate zone, called 'antipodeans', was disputed (considered heresy by the church).

Torrid zone (around the equator. Uninhabitable due to heat.)

Medieval maps: Initially, they did not use the concept of scale, nor of representing actual distances on the earth by distances (in the same ratios) on the paper.

Ex.: The T-O maps. (See p. 255 in the book). They are schematic. (In modern terms, we might say they only represent topology.)

Later development: Portolan charts. More like modern maps (more 'realistic').

Used for navigation at sea.

The lines show compass directions from one point to another. Useful in conjunction with a compass, which was invented around the 12^th century.

Does the earth rotate?

Rotation of the earth would produce the same astronomical observations. Important point: astronomers only observe relative motions.

Advantage of rotating earth: greater simplicity

Arguments against a rotating earth:

1. An arrow shot upward falls to the ground at the same spot. (Buridan's argument)

Oresme responds. Uses the example of a person inside a (perfectly smoothly) moving ship, who is unaware of the motion. (Compare to Galileo's argument.)

[2. If the earth were rotating, the centrifugal force would throw everything off the equator. (Ptolemy's argument)]

The Greek & Islamic Background to Western Astronomy

Differences between astronomy & cosmology:

Astronomy more mathematical. Derived from Ptolemy's Almagest.

Cosmology was more focused on physical considerations. Derived from other texts, such as Aristotle & the Bible.

Astronomical instruments:

Large quadrants (13^th c.)

Sextant (18^th c.)

Astrolabe. (From 100 b.c. Modified by Muslims to be used for astronomical calculations -- modified form included a simple map of the heavens & moving parts to simulate movement of heavenly bodies. (as in picture on p. 265 in the book)

Muslim astronomers criticize Ptolemy's astronomy, as lacking a physical basis.

Averroes wants to return to Aristotelian spheres.

Alhazen tries to reconcile Aristotelian spheres w/ Ptolemaic epicycles.

Astronomy in the West

In the early middle ages, there was little astronomical knowledge.

The Christians gained astronomical knowledge through contact w/ the Muslims in Spain, incl.:

the astrolabe, making quantitative astronomy possible

translations of ancient astronomical works, esp. Ptolemy, leading to the teaching of Ptolemaic astronomy in the schools.

Astronomical knowledge grows increasingly sophisticated after this (though confined to a relatively few practitioners).

Astrology

Astrology = the study of the effects of the heavens on the things on earth.

Observational evidence for the influence of the heavens on the earth:

Heavenly bodies are the source of light & heat

The seasons are connected w/ the sun's motion around the ecliptic.

The tides are connected w/ the moon's orbit.

The pole of the celestial sphere exercises magnetic attraction (compass needle points towards it).

Religious support:

The heavens have long been associated w/ divinity, and divinity has been thought to influence human affairs, going back to ancient times.

There was also a widespread belief that celestial events were 'omens' of terrestrial events, going back to ancient Mesopotamia. This eventually developed into the idea that the celestial configuration at the time of your birth indicated the future course of your life.

The Greeks also thought the heavens affected the earth.

Plato: the Demiurge delegated to the planetary deities the task of creating parts of the sublunar realm.

Aristotle: the Unmoved Movers were also the source of terrestrial motion.

Stoics: thought of the whole universe as an organic whole.

People (from ancient through medieval times) saw these sort of influences as of a piece with the influences the heavens allegedly exert on the weather, and on individual people.

Objections to astrology:

Augustine worried that astrological beliefs threatened the doctrine of free will.

Celestial influence on the body was ok, as long as one preserves freedom of the will.

This attitude was followed by medieval thinkers. The general view was that astronomical events did have an influence on human affairs in a general way, but that they did not determine an individual's decisions.

[ Philosophical reflection: This is another chapter in the perennial determinism / free will controversy. Free will has been threatened by (a) the Fates (in Greek mythology), (b) God's omniscience, (c) astrology, and today (d) modern biology, psychology, and/or physics. Are the modern fears of determinism better-founded than those earlier ones?]