Medieval Philosophy
Jean Buridan
We are now dealing of a period which is the rediscovery of Aristotle’s natural philosophy. In the 13th century there were many translations to latin of the aristotelian philosophical system.
They studied a lot of natural philosophy, like physics, astronomy, physiology, and cosmology.
Buridan made a commentary on Aristotle for example.
Buridan was a master of art. He studied theology, medicine in a ’unitary way’ as John Murdoch puts it. Different scholars in different faculties all share the same knowledge and textbooks as their starting points for learning.
Aristotle became an authority in the late 13th century. Aristotle was kind of a textbook for natural philosophy. With Buridan however we see a lot of critiques of Aristotle.
John William Draper and Andrew Dickson White wrote about medieval science in 1890s. They argued that there was a conflict between religion and science during the medieval ages. ”In speaking of christianity, referens is generally made to the roman church.. partly because it has commonly sought to enforce its demands by the civil power in the Vatican – and we hhave only to recall the inquisition.”
They think specifically of Galileo Galilei, one of the most important scientists of the modern age for using the telescope, and founding statics and dynamics – whilst also supporting heliocentrism.
In 1616 church forbids Galileo from teaching copernicanism, because there were certain passages of the bible which seemed to contradict the theory.
Galileo publishes his Dialogues on the Two Chief World Systems in 1632, where he paints the pope as a bastard. In the same year, the church bans Galileo’s work and places him under house arrest until his death. This has become one of the most famous conflicts between the religious powers and science. So for Draper and White, science and religion are incompatible. They therefore also conclude that since the middle ages were religious, they were not scientific.
In much this led to the history of science in large skipping the middle ages in their teaching. This is the way we learn it today.
Pierre Duhem was a physicist, philosopher of science and historian. He shows that the equivalence made by Draper and White does not work. Eg. Galilei and Copernicus were both fundamentally religious people. Etienne Tempier, the bishop of Paris in 1277, condemnds 219 philosophical statements which are actually the birth certificate of modern science. What is interesting about the propositions is that we cannot limit the divine freedom; 27: that the first cause cannot make more than one world. This is a principle from Aristotle. Tempier condemned this proposition because it limits the power of God. God could make lots of worlds. And 66: That God could not move the heaven in a straight line, the reason being that he would then leave a vacuum; no vacuum in Aristotle, therefore the universe could not be moved. For Tempier this limits God, of course God could do something like this. 17: That what is impossible absolutely speaking cannot be brought about by God or by another agent – this is erroneous if we mean something impossible according to nature. Aristotelian physics was considered as a kind of natural necessity – this is theway things are, but not the way things have to be. Natural vs. Logical necessity. God could have made things differently.
The condmnation was a license for medieval philosophers to think about the world outside of the Aristotelian way of thinking about the world.
The universe is of infinite duration, and of finite extension; it contains no vacuum. The universe is ordered very specifically according to the planets. Each of the spheres from the moon outwards rotate around the earth with uniform circular motion; the earth is motionless at the center of the universe. On Earth the elements go to their natural place. Such is the sublunary world. Fire and air go upwards, water and earth go downwards.
John Buridan was a master of arts. He taught at the university of Paris from 1325-1360. He decided not to become master of theology. He was also rector of the university twice. He wrote on logic, metaphysics, ethics, and natural philosophy.
Terms on projectile motion:
Nature: a source of motion intrinsic to the thing moved (usually substantial form).
Natural motion: motion in accordance with the nature of what is moved. Like fire moves up, and earth moves down.
Violent motion: motion caused by something external to what is moved.
Aristotelian principle: everything that is moved is moved by something else.
Second principle: no action at a distance, no vacuum, always carried by a medium.
In Aristotelian thought, what moves a projector after it leaves the projector is the so-called theory of antiperistasis. It holds that the proejctile swiftly leaves the place in which it was and nature, not permitting a vacuum, rapdily sends air in behind it to full up the vacuum. The air moved swiftly in this way and impinging upon the projectile impels it along further. This is repeated continually up to a certain distance.
Arisottle antiperistasis = reciprocal replacement. It is the air which gives the force until a certain point.
”But such a solution notwithstanding, it seems to me that this method of proceeding was without value because of many experiences.”
Roger Bacon in 1200s, scientia experimentalis > importance of experience, but in a wide sense: even internal illumination, personal experience.
John Buridan in 1300s, experiences > to observe a thing how it happens frequently to derive general rule but not modern experiment.
Galileo Galilei: experiments are quantitative > you do it in particular and controlled conditions, you use measurements and you repeat it.”
One very important thing about the condemnation of 1277, is that it allows God to actually have the ability to trick us. God can literally do anything, anything else is limiting. Some people even went so far in relation to this to hold that knowledge is probable, something that you cannot think in the strict aristotelian framework. This later leads to Descartes’ claim that there is a possibility for an evil genius and so on.
”The first experience concerns the top and the smith’s mill which are moved for a long itme and yet do not leave their places. Hence it is not necessary for the ari to follow along to fill up the place of departure of a top of this kind and a smith’s mill. SO it cannot be said that the top and the smith’s mill are moved by the air in this manner.”
This circular movement of the wheel remains even if there is no air to fill it up. So Aristotle’s position does not hold. And there are more experiences that agree with this observation of Buridan’s.
Buridan comes up with the idea of the Impetus instead. The impetus is a motive force of the moving thing. The impetus is impressed onto a thing by someone else, and the thing is launched according to the force that it has in itself, in the direction it was moved by the projector. The projector or motor leaves a force in the projectile. The more force with which t he projectile was launched, the greater the impetus. The impetus is what causes the projectile to keep moving after leaving the projector. The impetus is resisted by air and gravity, until it stops. The air and the gravity are impeti driving the object in two differing directions, down by the gravity, and opposite from the air which resists it.
What is impetus ontologically? It is a quality. ”the impetus produces the motion, impetus is a thing of permenanet nature. It is probable that the impetus is a quality naturally present and presiposed for moving a body in which it is impressed.” It is an accident.