The first wave of natural philosophers lived and thought between c. 600 and 400 b. c.e. They are called the Presocratics, although some of them were actually contemporaries of Socrates. All of them believed that the universe, or cosmos, could be explained through a consistent set of rules that could be grasped with either the senses or the mind. Although not atheists, they did attribute to nature, or physis, more mechanical explanations than did Homer or Hesiod. Each in his own way sought an arkhe—the original principle of existence and change (or lack of change, depending on the philosopher). For some, this might be air; for others, fire; or for others, even atoms. No original texts from these philosophers survive, and their words are preserved only in the writings of later philosophers and historians.
The person usually designated the first Greek philosopher was Thales of Miletos (625-585 b. c.e.). Concerning his astronomical work, he is famous for predicting a solar eclipse based on his own study of their periodic recurrences and, probably, having access to data kept in the Near East for the previous millennia. Likewise, he is credited with the theories that Earth was a "bubble" of air in the midst of an aqueous mass, that the light of the moon was actually reflected sunlight, and that all of creation was a form of water, which he believed was the cosmic arkhe. On a more metaphysical level, he argued that all creatures, even stones, had souls, and that this accounted for their ability to provoke movement. He was specifically referring to magnets when composing this theory.
Following in the wake of Thales was Anaximander, also of Miletos, who lived around 570 b. c.e. Contrary to Thales's views, Anaximander believed that the primordial arkhe was infinitude, from which all the "stuffs" of the universe came into being. These interacted with one another through contrasts of hot and cold. Like Thales, Anaximander believed that the Earth, as the center of the universe, was suspended in an immovable state, equidistant from every other point in the outer heavens (Barnes 1987, 37). The third great Milesian philosopher was Anaximenes, who followed many of Anaximander's precepts, but who believed that the arkhe of the universe was air (Barnes 1987, 37).
Coming after the Milesians were the Pythagoreans, so named for their founder, Pythagoras. In terms of astronomy specifically, Pythagoras was credited with figuring out the order of the then-known heavenly bodies: Earth, moon, Mercury, Venus, sun, Mars, Jupiter, Saturn (Nicolaidis 2001, 185). In terms of mathematics, he was said to have discovered the Pythagorean Theorem (a2 + b2 = c2), although this attribution was probably a later invention. In the realms of "abstract" philosophy, the Pythagoreans introduced the idea that the cosmos incarnated a rational order and divine harmony. They believed that below the moon was where generation, corruption, disorder, and general chaos held sway, and above the moon was an area of eternal order and purity. They believed that humans lived below the moon; the gods lived above.
Finally, Pythagoras and his followers propagated the ideology of metempsychosis, or what we might call reincarnation. Pythagoras suggested that unlike the body, the soul was immortal, and it passed into different bodies over the course of several lifetimes. In his Life of Pythagoras, the later philosopher Porphyry stated, "But it became very well known to everyone that he said, first, that the soul is immortal; then, that it changes into other kinds of animals; and further, that at certain periods whatever has happened happens again, there being absolutely nothing new; and that all living things should be considered as belonging to the same kind" (Barnes 1987, 86).
One of the most influential Presocratic philosophers was Heracleitus (late sixth century b. c.e.), occasionally called the Riddler because of the confusing nature of his theories. On a simple level, he believed that fire was the primordial arkhe. Somewhat more complex were his three most popular theories of reality: First, the world was eternal, rather than created or evolved as in Hesiod's Theogony. Second, everything in the world was always in a state of flux or change. Finally, and most obscurely, was the Unity of Opposites, whereby all things were manifestations of contradictory opposites whose tug-of-war was essential to their continued existence. Thus, "the world is an eternal and ever-changing modification of fire, its various contents each unified and held together by a dynamic tension of contrarieties" (Barnes 1987, 39).
The next wave of Presocratic philosophers—the Eleans—was led by Parmenides (c. 510-450 b. c.e.). As far as clarity goes, his work was not much better than that of Heracleitus. All his references to the natural sciences occur in a section of his poem On Nature, which he himself called the Way of Opinion, and which he claimed was false and deceitful. This caveat aside, he rejected the beliefs of the Milesians by claiming that there were actually two arkhai (pl. of arkhe), light and darkness, and that all things partook of both.
Concerning the structure of the universe, Parmenides argued that the cosmos was organized into rings or spheres. The innermost was the primary cause of creation and movement, which Parmenides identified as a goddess. Then came the ring of air, and then the sun and the Milky Way, which were exhalations of fire. Then there was the moon, composed of air and fire; the aither, or the sky; and finally the Earth itself, densest of them all (Allen 1985, 46). In his section called "True Things," Parmenides was more philosophical than scientific, focusing on epistemology, or the ability to know anything. He argued that reality did exist, and that all things were unchanging and graspable by the human mind.
Parmenides's two main followers were Melissos and Zeno, both of whom involved themselves in questions of the infinite. Melissos argued that existence was infinite and filled with only one, unmoving "thing." In a similar vein, Zeno, in his forty-odd series of arguments, suggested that existence was a unified entity. If more than one "thing" existed, paradoxes, which were impossible, would follow. Both philosophers believed that human perceptive senses (sight, smell, etc.) were deceptive and could not be used to comprehend reality.
The last Presocratics were Empedocles of Acragas (493-433 b. c.e.), Anaxagoras of Athens (500-428 b. c.e.), and Democritus of Abdera (born c. 460 b. c.e.), often called the Pluralists. Empedocles was the first to suggest that all creation was composed of the four elements—air, fire, water, and earth. The impetus for their mixing or dissolution was love (philia) and strife (neikos). The cosmos, he taught, began with the separation of these elements and the formation of light and darkness.
Anaxagoras argued that all creation emerged from one universal mass, which underwent a period of differentiation leading to the apparently different "stuff" now composing the cosmos. However, Anaxagoras held that none of this "stuff" was totally separated from all the other "stuff," so that all creation contains bits of all the rest of creation. As such, there was, say, a bit of iron in blood, and a bit of gold in iron. The mover and shaker of all these "stuffs" was Mind (Nous), the one thing in the universe that was eternal and unchanging. This Mind set all things into motion, with the dense, moist, cold, and dark heading together into a "center" (basically, Earth), while their opposites went to the periphery (heavens). The one exception was "heavy" stars, which, according to Anaxagoras, were stones torn from Earth, rendered red-hot by their swift motion.
Democritus argued that all reality was made up of very tiny, indivisible parts, which come together in different ways to make up the stuff of the universe. In many respects, then, he was the father of modern atomic (a = not, to-mos = cut apart) theory. Beyond the "hard" sciences, Democritus was also a fan of anthropology, and he wrote on such topics as the origins of religion and the nature of language (Barnes 1987, 47).
All the Presocratics worked in a bit of a vacuum. Although they had access to each other and to data from the Near East, such issues as eschatology and the reliability of the senses were new to the world of philosophic inquiry: A person, or a civilization, has to have a lot of leisure time to start considering whether reality exists or not. To their credit, the Presocratics established the idea that the universe was governed by laws, laws that were applicable to all aspects of reality. They tested their hypotheses of these laws, rather than just accepting them. And they did teach people to question their assumptions about reality, leading ultimately to the understanding that the Earth is not the center of the universe, and that, as quantum theory now tells us, the observer is an integral component of any observation.
World History
