They were looking for the underlying laws of nature. They wanted to understand what was happening around them without having to turn to the ancient myths. And most important, they wanted to understand the actual processes by studying nature itself. This was quite different from explaining thunder and lightning or winter and spring by telling stories about the gods.
So philosophy gradually liberated itself from religion. We could say that the natural philosophers took the first step in the direction of scientific reasoning, thereby becoming the precursors of what was to become science.
Only fragments have survived of what the natural philosophers said and wrote. What little we know is found in the writings of Aristotle, who lived two centuries later. He refers only to the conclusions the philosophers reached. So we do not always know by what paths they reached these conclusions. But what we do know enables us to establish that the earliest Greek philosophers’ project concerned the question of a basic constituent substance and the changes in nature.
THREE PHILOSOPHERS FROM MILETUS
The first philosopher we know of is Thales, who came from Miletus, a Greek colony in Asia Minor. He traveled in many countries, including Egypt, where he is said to have calculated the height of a pyramid by measuring its shadow at the precise moment when the length of his own shadow was equal to his height. He is also said to have accurately predicted a solar eclipse in the year 585 B.C.
Thales thought that the source of all things was water. We do not know exactly what he meant by that, he may have believed that all life originated from water—and that all life returns to water again when it dissolves.
During his travels in Egypt he must have observed how the crops began to grow as soon as the floods of the Nile receded from the land areas in the Nile Delta. Perhaps he also noticed that frogs and worms appeared wherever it had just been raining.
It is likely that Thales thought about the way water turns to ice or vapor—and then turns back into water again.
Thales is also supposed to have said that “all things are full of gods.” What he meant by that we can only surmise. Perhaps, seeing how the black earth was the source of everything from flowers and crops to insects and cockroaches, he imagined that the earth was filled with tiny invisible “life-germs.” One thing is certain—he was not talking about Homer’s gods.
The next philosopher we hear of is Anaximander, who also lived in Miletus at about the same time as Thales. He thought that our world was only one of a myriad of worlds that evolve and dissolve in something he called the boundless. It is not so easy to explain what he meant by the boundless, but it seems clear that he was not thinking of a known substance in the way that Thales had envisaged. Perhaps he meant that the substance which is the source of all things had to be something other than the things created. Because all created things are limited, that which comes before and after them must be “boundless.” It is clear that this basic stuff could not be anything as ordinary as water.
A third philosopher from Miletus was Anaximenes (c. 570—526 B.C.). He thought that the source of all things must be “air” or “vapor.” Anaximenes was of course familiar with Tholes’ theory of water. But where does water come from? Anaximenes thought that water was condensed air. We observe that when it rains, water is pressed from the air. When water is pressed even more, it becomes earth, he thought. He may have seen how earth and sand were pressed out of melting ice. He also thought that fire was rarefied air. According to Anaximenes, air was therefore the origin of earth, water, and fire.
It is not a far cry from water to the fruit of the earth. Perhaps Anaximenes thought that earth, air, and fire were all necessary to the creation of life, but that the source of all things was air or vapor. So, like Thales, he thought that there must be an underlying substance that is the source of all natural change.
Nothing Can Come from Nothing
These three Milesian philosophers all believed in the existence of a single basic substance as the source of all things. But how could one substance suddenly change into something else? We can call this the problem of change.
From about 500 B.C., there was a group of philosophers in the Greek colony of Elea in Southern Italy. These “Eleatics” were interested in this question.
The most important of these philosophers was Parmenides (c. 540-480 B.C.). Parmenides thought that everything that exists had always existed. This idea was not alien to the Greeks. They took it more or less for granted that everything that existed in the world was everlasting. Nothing can come out of nothing, thought Parmenides. And nothing that exists can become nothing.
But Parmenides took the idea further. He thought that there was no such thing as actual change. Nothing could become anything other than it was.
Parmenides realized, of course, that nature is in a constant state of flux. He perceived with his senses that things changed. But he could not equate this with what his reason told him. When forced to choose between relying either on his senses or his reason, he chose reason.
You know the expression “I’ll believe it when I see it.” But Parmenides didn’t even believe things when he saw them. He believed that our senses give us an incorrect picture of the world, a picture that does not tally with our reason. As a philosopher, he saw it as his task to expose all forms of perceptual illusion.
This unshakable faith in human reason is called rationalism. A rationalist is someone who believes that human reason is the primary source of our knowledge of the world.
All Things Flow
A contemporary of Parmenides was Heraditus (c. 540-480 B.C.), who was from Ephesus in Asia Minor. He thought that constant change, or flow, was in fact the mosf basic characteristic of nature. We could perhaps say that Heraclitus had more faith in what he could perceive than Parmenides did.
“Everything flows,” said Heraclitus. Everything is in constant flux and movement, nothing is abiding. Therefore we “cannot step twice into the same river.” When I step into the river for the second time, neither I nor the river are the same.
Heraclitus pointed out that the world is characterized by opposites. If we were never ill, we would not know what it was to be well. If we never knew hunger, we would take no pleasure in being full. If there were never any war, we would not appreciate peace. And if there were no winter, we would never see the spring.
Both good and bad have their inevitable place in the order of things, Heraclitus believed. Without this constant interplay of opposites the world would cease to exist.
“God is day and night, winter and summer, war and peace, hunger and satiety,” he said. He used the term “God,” but he was clearly not referring to the gods of the mythology. To Heraclitus, God—or the Deity—was something that embraced the whole world. Indeed, God can be seen most clearly in the constant transformations and contrasts of nature.
Instead of the term “God,” Heraclitus often used the Greek word logos, meaning reason. Although we humans do not always think alike or have the same degree of reason, Heraclitus believed that there must be a kind of “universal reason” guiding everything that happens in nature.
This “universal reason” or “universal law” is something common to us all, and something that everybody is guided by. And yet most people live by their individual reason, thought Heraclitus. In general, he despised his fellow beings. “The opinions of most people,” he said, “are like the playthings of infants.”
So in the midst of all nature’s constant flux and oppo-sites, Heraclitus saw an Entity or one-ness. This “something,” which was the source of everything, he called God or logos.
Four Basic Elements
In one way, Parmenides and Heraclitus were the direct opposite of each other. Parmenides’ reason made it clear that nothing could change. Heraclitus’ sense perceptions made it equally clear that nature was in a constant state of change. Which of them was right? Should we let reason dictate or should we rely on our senses?
Parmenides and Heraclitus both say two things:
Parmenides says:
a) that nothing can change, and
b) that our sensory perceptions must therefore be unreliable. Heraclitus, on the other hand, says:
a) that everything changes (“all things flow”), and
b) that our sensory perceptions are reliable.
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