Aristotle - York University

Aristotle - York University

Aristotle Knowledge comes from experience SC/NATS 1730, VII 1 Aristotle 384 - 322 BCE Born in Stagira, in Thrace, near Macedonia.

The Stagirite. Son of Nichomacus, prominent physician. Aristotle was likely trained in medicine. SC/NATS 1730, VII 2 Platos Student At age 17, Aristotle

was sent to study with Plato at the Academy. He became Platos most important student, remaining at the Academy 20 years, until Platos death. SC/NATS 1730, VII 3 Aristotle becomes a royal tutor. When Aristotle left the Academy in 347, he settled briefly on islands near the Ionian coast, then accepted an

invitation to teach the son of the Macedonian king, Philip II, whose father had been attended by Aristotles own father. SC/NATS 1730, VII 4 Alexander the Great Aristotle tutored Phillips son, Alexander, for 5 years until Phillip died and Alexander assumed the

throne. Alexander went on to conquer much of the nearby world. SC/NATS 1730, VII 5 The Lyceum In 335 BCE, Aristotle returned to Athens and established his own school, in competition with the Academy.

Named the Lyceum, as it was adjacent to the temple to the god Apollo Lykaios. Morning serious lectures Evening public lectures Inclusive curriculum Classification approach Aristotle associated with Alexander After Alexander's death in 323, Aristotle fled Athens to prevent a second sin against philosophy. SC/NATS 1730, VII 6

Aristotles works What we have as Aristotles works are about 30 closely written, terse, treatises on a full range of philosophical and scientific topics. These may have been his morning lectures, or even students notes on those lectures. SC/NATS 1730, VII 7 versus Platos works

In contrast, Platos surviving works consist of about 20 dramatic dialogues that discuss philosophical issues in a Socratic, dialectical, questioning manner. Aristotle may have written such works as well, but they have not survived. SC/NATS 1730, VII 8 The foundation of western philosophy and science Aristotles works more than Platos laid

the groundwork for the systematic development of philosophy and the basic framework for the understanding of nature. Logic, empirical evidence, systematic explanation. Sound methodology, wrong conclusions. SC/NATS 1730, VII 9 The benchmark for the understanding of nature

The standard view of the world for 2,000 years. To understand the development of science it is necessary first to grasp Aristotles methods and his conclusions about nature. SC/NATS 1730, VII 10 Empiricism First, Aristotle grounds all knowledge on experience.

This is unlike Plato for whom knowledge came only when the philosopher escaped from the world of sense perception, which could mislead. Reality, for Aristotle, was the world around us, not the objects of the mind, which could be just fantasy. SC/NATS 1730, VII 11 Aristotle, the biologist

Students at the Lyceum collected specimens, dissected, and classified them. Analysis of life forms arose from examination of many real examples. Similarly every subject was examined and classified. SC/NATS 1730, VII 12 Contrasting World Views A basic division in how the world is understood: Plato (pointing up) true knowledge comes from contemplating the abstract

ideas. Aristotle (pointing down) true knowledge comes from close examination of the world around. SC/NATS 1730, VII Plato and Aristotle from Raphaels School of Athens. 13 Contrasting World Views, 2 The ideal form, an example: For Plato, a geometric object, e.g. a triangle, circle, cube, etc.

The true object exists only in the mind. Actual representations are only approximate. For Aristotle, an animal or plant species, e.g. roses, trout, human beings, etc. The species is what all the instances of it have in common. SC/NATS 1730, VII 14 Logic

The way to knowledge beyond what is presented to the senses. Based upon Parmenides principle of the excluded middle. A statement is either true or false. Therefore, if it can be shown that a statement is not true, it must be false. If valid reasoning leads to a false conclusion, one of the premises must be false. SC/NATS 1730, VII 15 Syllogisms

The key component of Aristotelian logic is the syllogism. Typical format: Major premise a general truth, or observation Minor premise a particular fact, or specific observation Conclusion an inference implied by the two premises together SC/NATS 1730, VII

16 Syllogisms, 2 The classic example of the syllogism: Major premise: All men are mortal. Minor premise: Socrates is a man. Conclusion: Socrates is mortal. In other words, what applies to all members of a group applies to each and every

member. SC/NATS 1730, VII 17 Syllogisms and Logic Aristotle worked out the forms of valid reasoning from premises. The principle is to combine known truths and deduce new knowledge that must be true if the premises are true. The method is sound.

SC/NATS 1730, VII 18 However The conclusions from syllogistic reasoning must be true only if the premises are true. Very often, Aristotle reasoned correctly from faulty generalizations and produced impressively argued, but nevertheless false, conclusions. As Plato noted, the senses can deceive.

SC/NATS 1730, VII 19 The Four Causes A cause for Aristotle is a factor that partly determines a result. Aristotle identified four causes as the explanation for anything (or event) that is. How and why something came to be is understood by examining its four causes.

SC/NATS 1730, VII 20 The Four Causes, 2 The causes are: The Material Cause basically the stuff out of which anything is made. The Formal Cause the form, size, and shape

of the thing. The Efficient Cause what put the material into the form it is in. The Final Cause the purpose of the thing. SC/NATS 1730, VII 21 The Four Causes, 3 An example: The causes of a knife.

Material: The metal, e.g. iron, steel. Formal: The shape of a knife sharp edge, long shaft, pointed end, rounded handle, etc. Efficient: The tool maker that fashioned it. Final: To cut or slice. SC/NATS 1730, VII 22 The Four Causes, 4 Man-made things are easy enough to classify, but natural objects become more difficult.

What is the efficient cause of a tree? What is the final cause of a rain shower? Or a human being? What is the material cause of a thunderclap? The formal cause of sunlight? SC/NATS 1730, VII 23 The Four Causes, 5 For Aristotle, the most important cause was the final cause, that for which the thing exists. Anything is explained only by

understanding its purpose. Examples: a chair, a blackboard, a piece of chalk, a shoe. Or, a planet, a drought, a mountain, a leopard. SC/NATS 1730, VII 24 Aristotles logical analysis applied From the logical tools developed by

Aristotle, and the careful observations made and generalized, Aristotle built a complete system that explained the world as it is. His system shows the power of reasoning and the dangers of premature generalizations. SC/NATS 1730, VII 25 Aristotles Cosmos Classification: There are two different parts of the world.

There is the world all around, where things come and go; are born, live, and die; and motions start and stop. There is the world up in the sky, where things happen over and over again: the sun rises and sets, the seasons reoccur, the planets repeat cycles. SC/NATS 1730, VII 26 The Sub-Lunar World

The world around us includes the Earth itself, the seas, the atmosphere, and of course fire. It extends up to the moon, the first heavenly body. SC/NATS 1730, VII 27 Generation and Corruption The Sublunar world is the world of life. Everything in it came into being, had a period of existence, and died.

Even motions started and stopped. Even objects that did not appear to have a life span were subject to this process: Rocks, mountains, etc., came into being and passed away, though over very long periods. SC/NATS 1730, VII 28 The Material of the Sublunar World Aristotle accepted the popular four

elements of Empedocles as the material of the sublunar world: Earth, Air, Fire, Water. Everything in the sublunar world is made up of these elements, in different combinations. SC/NATS 1730, VII 29 Natural Place

The elements all have a natural place in the sublunar world Earth and water are heavy and so their natural place is at the centre of the world. Fire and air are light and their natural place is at the outer edge of the sublunar world. Note: Light does not mean less heavy. SC/NATS 1730, VII 30 Natural Motion

When unobstructed, the elements strive to reach their natural place. This is called natural motion, and requires no further explanation. Earth is heavier than water, so it will push past water seeking the centre. Fire is lighter than air, so it pushes further outward. SC/NATS 1730, VII 31 The Sublunar World

SC/NATS 1730, VII 32 Forced Motion Objects on Earth are not always in their natural place, nor do they only have natural motion. They may be forced to move unnaturally, by, for example, being pushed or pulled. Or an object may be prevented from going to its natural place by being held back.

SC/NATS 1730, VII 33 Everyday Forced Motions A heavy object may be pulled or pushed to a new location. When it is no longer being forced, it stops. If it is pushed off a cliff, it will resume its natural motion downward, seeking its natural place. A light object, e.g. a vessel containing air,

may be pushed under water If released will assume its natural motion upward. SC/NATS 1730, VII 34 The Problem with Logic Aristotles view of the world is complete and consistent. It is based on direct observation, and logical analysis. When something cannot be observed (e.g. a cause), Aristotle endeavours to discover

what it must be, by reasoning from what he has already determined. SC/NATS 1730, VII 35 Not so obvious forced motions The weakness of Aristotles view of the cosmos is revealed most clearly in his analysis of forced motions. Aristotle believed that an object would only move unnaturally, if it was pushed or pulled i.e. was in direct contact with the cause of motion.

SC/NATS 1730, VII 36 What about something thrown or shot? Consider a rock being hurled, or an arrow shot from a bow. The motion of the object fits Aristotles analysis, only so long as it is in contact with the cause of motion the throwing arm or the bowstring. SC/NATS 1730, VII

37 Why does the object move through the air? According to Aristotle, the object resumes its natural motion (i.e. straight down) as soon as it is no longer in contact with whatever was forcing it. But this is obviously not so; it keeps going. SC/NATS 1730, VII 38 Aristotles Answer:

Since the world is full (no empty spaces anywhere), a rock or arrow flying through the air must be pushing the air out of the way as it flies. That air has to go somewhere. It goes behind the moving object and continues to push it forward. SC/NATS 1730, VII 39 Antiperistasis

This is the principle of antiperistasis against remaining in the same place. SC/NATS 1730, VII 40 The weakest point in Aristotles physics Aristotles antiperistasis argument was the most obviously contrived explanation in his physics. It attracted the attention of later philosophers almost immediately as a

problem. SC/NATS 1730, VII 41 The Super-Lunar World The heavens were obviously different. Motions there repeated over and over again. Generation and corruption did not apply.

Heavenly objects seemed to always be there. What needed explaining were the cycles. SC/NATS 1730, VII 42 Natural Motion in the Super-Lunar World In the sublunar world, objects moved to their natural place (and then stopped). In the superlunar world, they cycled.

Therefore natural motion in the superlunar world must be circular. The circle moves, but stays in the same place. SC/NATS 1730, VII 43 The Material of the Super-Lunar World The materials of the sublunar world have built in tendencies to go to their natural places.

Therefore the material of the superlunar world must be different. SC/NATS 1730, VII 44 The Quintessence There are no forced motions or contrary tendencies in the heavens, so there is only one material there. It is an additional and different element. Aristotle called it the Fifth Element.

In Latin, that is the Quintessence. SC/NATS 1730, VII 45 The Crystalline Element The heavens must be full (no empty space), but they look like they are empty. Solution: The fifth element must be invisible, like glass, except for the few bits that show up, the planets and the stars. SC/NATS 1730, VII

46 The Problem of the Planets, again All the natural motions of the fifth element are circular. Since there are no forced motions, everything in the heavens must be moving in combinations of circular motions. SC/NATS 1730, VII 47 Eudoxian Spheres

Aristotle adopted the scheme of Eudoxus with spherical shells nested inside each other, all turning different ways. But with a difference: Eudoxus was happy to describe the motions geometrically. Aristotle required a cause of motion. SC/NATS 1730, VII 48

Solution: More spheres Eudoxus thought 27 spheres were enough to account for the motions of the celestial sphere and the seven planets (which include the sun and moon). But their motions were independent. Aristotle required that motion be communicated from one to another. He needed 55 spheres in total. SC/NATS 1730, VII

49 The Unmoved Mover The ultimate cause of motion in the universe is what turns the celestial sphere. The celestial sphere rubs up against the spheres of Saturn, which rub up against Jupiter, etc. That ultimate cause is the Unmoved Mover. SC/NATS 1730, VII 50

The Aristotelian Cosmos An illustration from an edition of Aristotles On the Heavens, published in 1519. SC/NATS 1730, VII 51 A Philosophy for 2000 Years

Aristotles scheme provided a logically consistent explanation for the motions of the heavens and life on Earth. It combined most of the preconceptions of his time into a grand system. His view remained the standard conception for nearly 2000 years. SC/NATS 1730, VII 52

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