History Weblecture for Unit 8
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We shift from the river valleys of Egypt and Mesopotamia to the smaller cities of Asia Minor in what is now Turkey, and the peninsula of Greece. By the seventh century bce, the area on both sides of the Aegean Sea was inhabited by people speaking Greek, who lived and worked in small city-states that thrived on trade. Asia Minor in particular had become a crossroads for trade between central Europe, the Mesopotamian valleys, and the Mediterranean kingdoms of the Phoenicians and the Egyptians. The tradesmen carried spices, precious metals, jewels, tools, and new ideas from the eastern empires, and traded them for furs, lumber, and even tin shipped from as far away as Britain, to create the new metal bronze. From Egypt and Babylon, and later Assyria, they also brought tales of strange lands, bizarre animals, and the records of a thousand years of astronomical events to minds eager to find a rational relationship in the patterns of the stars.
If you are not familiar with this area, you may want to look at this map of Ionian City States, which shows the kingdom of Macedonia (Alexander the Great), the kingdom of Pergamum, and the Seleucid Kingdom (the kings inherited this kingdom from Alexander). Be sure that you can find the important cities like Miletus, where Thales was born, and Ephesus, the city St. Paul visited in his missionary travels.
Some of their stories found their way into the works of the Greek historian Herodotus. Others influenced the thinkers of the Greek city-states on the Ionian coast of western Asia Minor. From about 600 B. C. until nearly 400 B. C., these philosophers tried to determine the whatness of matter, the nature of mathematics, or the ultimate source of all motion in the universe. The earliest philosopher of this group, called the Presocratics because they lived before Socrates of Athens, was Thales of Miletus, who reputedly predicted the eclipse of 585 bce While we know very few details about Thales' life or his sources, and we have none of his own writings, we do have citations in the works of other philosophers. Aristotle mentions Thales several times in his Metaphysics. Thales seems to have been the first influential philosopher to generalize about the cause and effect in nature, and to try to come up with definitions or descriptions that would apply to all cases of an event, or all instances of a particular thing.
This practice makes an assumption, one of the most basic (and almost unmentioned, because we take it for granted) conceptions we have about the universe: Nature is ordered. We believe that natural events follow rules, and these rules can be discovered by thinking rationally about the limits and possibilities of a given situation. Thales' approach didn't make use of experimentation or directed observation: he used a method of working from premises to their logical conclusion. Since he didn't require that anyone rigorously test his premises, his methods led, as we shall see, to some startling and misleading results. Thales' methods are still used, though, in the thought experiments of the twentieth century physicists like Albert Einstein and Stephen Hawking, where we must imagine situations involving relativistic factors because we have no way to manipulate objects and do experiments under the necessary conditions.
Read about Thales at the St. Andrews Mathematics site.
Thales made a distinction between the essential attributes of a thing, which make it a particular kind of thing, and the accidental characteristics, which make it unique. His theory is sometimes stated briefly as "all is water", that is, all matter shares certain basic characteristics similar to those of water (such as three states, solid, liquid, and matter). The philosophers who followed Thales disagreed with his conclusions, but adopted his approach: they all try to discover the essential thing that makes matter matter and not something else like space or energy or force.
Anaximander was apparently aware of Thales' work, as he came from the same town and lived about the same time. We actually have at least one fragment directly attributed to Anaximander. From this and other citations of his thinking, we know that Anaximander offered a very different idea of matter. Instead of concentrating on the "wetness" of things, as Thales did, Anaximander sought a more balanced approach and concluded that the primary substance a dynamic tension between opposites, infinite and boundless, which had separated into matter. Anaximander is the first philosopher to consider that the universe might be infinite in origin. He also thought that the earth floated unsupported in space, surrounded by wheels like those of a chariot. These wheels were pierced in places, and the primordial fire shown through the holes, appear to us as the sun, moon, and stars.
Read the fragments of Anaximander and Aristotle's comments on his vision of the universe.
Anaximenes was also a Milesian, and thought to be a student of Anaximander. Like Thales, he believed the world was made of a single substance, but he chose air as his model of boundless stuff from which all other matter comes, because air can be compressed and rarefied. In successive stages of compression, hotter air is fire, and cooler air becomes water, then earth. He also thought that air was associated with life and the soul, and therefore necessary as a component of all living things. His theory differs significantly from Thales' concept in that Anaximenes believed that his primary substance could change form.
One of Anaximenes' followers was Heraclitus, who concentrated on the concept of change. Heraclitus understood that while individual drops of water in a river are constantly changing, the river form stays the same over time. He thought that matter was a junction of the characteristics of hot changing to cold, and wet changing to dry: different levels of these states produced different forms of matter, but no form of matter was ever static.
With Xenophanes, we start to see a different take on the question "what is stuff?" Xenophanes became a teacher in the school of Pythagoras near Elea in Italy, and produced many poems that still survive. He introduced the idea that the universe was infinite in age as well as extent, and was itself divine, in contrast to the created world of Greek mythology. He thought of God as part of nature, not separate from it.
This was a definite contrast to the world model proposed by Pythagoras, who held that the world was material, but perfectly made. The most perfect of all shapes in symmetry and mathematical simplicity is the sphere, because every point is exactly the same distance from the center. Thus the world, or cosmos, by which Pythagoras meant the whole universe, was limited in extent and took the the shape of a sphere. To balance the material earth, which he thought floated in space around the sun, there must be another earth-like world on the opposite side of the sun.
One of Xenophanes' students was Parmenides, who became a champion of the idea of a "real" world that was unchanging, without beginning or end, and that could not be destroyed. Parmenides thought that human perception was limited and led one to assume change where change did not actually exist. The real world is the essential world; we perceive only its accidents. Parmenides raised serious questions about the limits of human perception, that ask if it is even possible to know something about an objective reality.
Still yet another philosopher from Elea was Zeno, a pupil and friend of Parmenides. Like Parmenides, he was fascinated with the problem of change and the perception of reality, and like Parmenides, believed that everything was really part of one essence. He put together a list of paradoxes which aimed to show that the concepts of motion and plurality were ultimately inconsistent, and led to contradictions that required the assumption of continuous matter throughout all space and time. One of the most famous paradoxes involves running a race. Before you travel the entire race distance, you must reach the halfway point. But before you can reach the halfway point, you must reach the halfway point to the halfway point, one-fourth the distance of the whole race course. In his mathematical zeal, he realized that each length could be divided in half, and came to the conclusion that you could never move at all. While he achieved what to our minds is an absurd conclusion, Zeno raised a question about limits and the nature of magnitudes or sizes of things that Newton would eventually address when he discovered the calculus of numbers.
It is very important to realize that what Democritus meant by atoms and what we now call atoms were very different objects. A Democritan atom cannot be further divided into smaller particles or structures: it is the ultimate indivisible substance, the smallest possible particle of matter imaginable. Our modern atom, by contrast, is divisible (usually with the release of a great deal of energy), and by latest count, can be broken down into over 150 different kinds of sub-atomic particles.
With Leucippus and Democritus, we seem to break onto more familiar territory. Leucippus was associated with the Eleatic school of philosophers, and was a contemporary of Zeno. He and his more famous pupil, Democritus, believed that matter could be broken down into smaller and smaller pieces until finally one had individual particles that could not be cut apart any further, a-tomi. Democritus also taught that the Milky Way was made of individual stars, and that the universe might contain many other inhabited worlds, scattered in an infinite void. He thought the real properties of atoms governed our perceptions of them: sharp pointy atoms make up spices and acids, which taste "sharp" to us, and other atoms form solids by hooking onto one another. Democritus influenced the later philosophers Epicurus and Lucretius, both of whom proposed models of the universe based in the atomic theories of Democritus. Ultimately his theories were rejected because there was at the time no way to make any observations to substantiate his claims.
Having trouble keeping details about all these philosophers straight? You may find this Scholars Online YouTube video helpful..
Now, before you panic, there are some basic ideas that you need to remember from all of this, that are more important than which philosopher thought what....although you need to study that, too! These three groups of philosophers -- the Milesians, the Eleatics, and the atomists, all had some philosophical ideas in common.
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