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1. The Presocratics

This book is an introduction to the turning point in the that began in ancient Greece over twenty-five hundred years ago. Starting with the discovery of the concept of nature (physis), and then the ethical of and his followers, human began to reflect critically about themselves and the universe in which they lived. The first of Western history were the Presocratics, so named by later historians because they came before the pivotal figure of ancient philosophy, Socrates. The great achievement of the Presocratics was to discover the philosophical ideas of nature and , and to begin to articulate a scientific understanding of the universe. The leading Presocratic philosophers were the Milesians, the Pythagoreans, , and Zeno, and , and the Atomists.

The Milesians: Science and Nature Roughly speaking we can say that before the Milesians, the ancient Greeks experienced the world as filled with gods and divine spirits who were closely identified with parts or aspects of both nature and culture. Zeus was manifest in the sky and lightning, and law, Poseidon in the storms and the sea, Aphrodite in sexual passion, Iris in the rainbow, Demeter in the ever- returning grain, Hera in childbirth, feminine wisdom, Apollo in religious purity and self-restraint, Dionysus in wine and ecstasy, etc. There were river gods and spirits of sacred groves, there were earth-deities, there were presences and powers filling an enchanted universe. After the Milesians, educated Greeks and Romans began to think of nature (physis) as a realm with laws of its own, distinct from the gods, and of and as deriving from observation and reasoning, rather than ancestral tradition and law. This was the beginning of science and of a scientific, secular conception of nature and knowledge. The objective world of natural science (logos) replaced what came to be seen as a subjective world of religious imagination (mythos). 2

There are two ways in which intellectual historians have described the Milesian discovery. The first involves a new idea of how to acquire knowledge of the world. The Milesians were also the first methodological naturalists, the first to insist that scientific knowledge of the world must be acquired by observation and reasoning (as opposed to the hearsay of myths, traditions, sacred books, seers, dreams and voices sent by the gods). Whereas the Greek religious tradition based its claim to truth (revelation) on faith in ancestral authority and the claim of divine inspiration, the Greek scientific tradition based its claim to truth on evidence gained from sense- (empeiria). (Later, the theory that all knowledge was acquired this way was called .) The scientific method relies on the sensory world for its facts and on human reason to organize, interpret and explain those facts in terms of general laws. This is what gives science its objective character, what allows scientists from China or India or the US all to engage in science together, and not fall into methodological conflicts, even if they disagree wildly about art, , politics or religion. By contrast, people of different religions have different foundations for —their sacred authorities assert non-naturalistic ways of founding truth, their Gods command different laws and and practices. This is part of the reason why religious disputes can seldom be decided by rational means. They are not open to a common, objective method of testing and thereby falsifying or verifying the truth-claims of the opposing religious beliefs. The idea of methodological includes a new conception of truth (based on proof) vs. that of revelation (based on sacred authority). The other aspect of the Milesian discovery invokes a new conception of . In this respect, the Milesians were the first metaphysical naturalists, i.e. the first thinkers to claim that everything that exists derives from a common ground of natural substance, that the world is one material whole—the earth, the sky, the water, the air, fire, plants, animals, stars, humans, clouds, artifacts, everything. We can understand how this idea might arise in a society in which various types of technical knowledge were well advanced, and there was travel and trade between people of different cultures. The Greeks who built strong sea-faring ships, studied the movements of the stars at night, learned the material principles that allowed them to construct large buildings, dissected the human body and discovered medications for disease—they might well begin to wonder if “Zeus” really was present in lightning, “Poseidon” in the storm at sea, or “Apollo” in disease. As they intermingled with Egyptians and Babylonians and Scythes whose gods and customs were very different from their own, a new thought began to dawn: the idea of nature.

QUESTION: You cannot be a scientist unless you embrace methodological naturalism, but what about ? Does a scientist have to be a metaphysical naturalist? 3

How did Milesian natural science and philosophy develop?

Thales of

We have just four quotes from Thales:

1. All things are water (hydor). 2. The earth rests on water. 3. All things are full of gods. 4. The magnet has a soul.

These statements seem inconsistent with the naturalistic viewpoint I have been attributing to the Milesians. But if read in contrast to the world of the Greek polytheistic religion, they take on a naturalistic meaning. Thus the Greek word hydor probably meant not water as we understand it, but something more like “flowing liquid matter,” the fluid source or nutrient glue of the living, self-moving natural world. This implies that Thales conceived of “all things” as one unified and animated whole—as a biosphere nurtured by water (); as originating in water (cosmogony); or as made out of water (constituent analysis). This is the idea of one natural universe—the idea I have called metaphysical naturalism. Thales’ bottom-up conception of the structure of the natural world, which he bequeathed to his successors, had this form:

Laws of nature governing / \ Changing physical world (ta panta, “all things”) / \ originating out of / \ , the unchanging (arche, “source” or “principle” = hydor)

Since everything arises from or is composed out of the underlying material substance (Thales’ hydor, i.e. “flowing liquid matter”, ’s apeiron for 4

“the indefinite,” Anaximenes aer for “air” or “space”), there are no non- corporeal beings, i.e. no gods or immortal souls or anything of that kind. Thales’ other quotes also fit this scientific vision. “The earth rests on water” suggests there is a natural explanation of the earth’s place in the universe, in contrast to the myth of it resting on the shoulders of Atlas. Even the statements that “all things are full of gods” and “the magnet has a soul” can be interpreted naturalistically—“soul” (psyche) now simply meaning a natural animating or self-moving principle in matter, gods (theoi) now pointing to ever- recurrent natural laws and powers. These interpretations are consistent with the direction Thales’ students took in developing his naturalistic vision, beginning with Anaximander.

Anaximander Anaximander (610-546 BC) is credited with being the first person to make a map of the entire earth; to study human embryos; and to conceive of the universe as spherical in shape. We have a fairly large body of fragments from him, which reveal a far-ranging scientific mind. Here are some of the statements attributed to Anaximander:

1. The first principle and origin of being is neither water nor any of the other things called elements, but some other nature which is unlimited (a-peiron), out of which come to be all the heavens and the things in them.

2. What arose from the eternal [the apeiron] and is productive of hot and cold was separated off at the coming-into-being of this cosmos, and a kind of sphere of flame from this grew around the dark mist about the earth like a bark about a tree. When it was broken off and enclosed in circles, the sun, moon, and stars came to be.

3. The first animals were produced in moisture. When these water-creatures came out onto the land, their protective covers broke off, and they lived a different sort of life. The first humans arose from fish or fish-like creatures.

4. The earth is round and cylindrical, three times as long as in diameter. The circle of the sun is 27 times that of the earth, the moon 18 times that of the sun.

5. The things that are perish into the things out of which they come to be, according to necessity, for they pay penalty and retribution to each other for their injustice in accordance to the ordering of time.

What is the significance of these quotations? The first quote suggests that Anaximander, like Thales, may have conflated the ideas of metaphysical and methodological . In any case, for the Milesians scientific knowledge of nature begins with the principle that there is an underlying physical substance to all things, which Anaximander 5 conceives of as indeterminate (implied by the transformation into one another of elementary bodies such as earth, air, fire and water). It is also interesting that Anaximander’s idea of the Apeiron (Un-limited or Bound-less) seems to have arisen from criticism of Thales’ view of hydor, a determinate form of matter, as the underlying reality. This suggests that Thales encouraged his students to develop their own theories, rather than submit to his. Greek science was from the beginning an evidence-driven and self-critical communal enterprise, rather than one based on authority and dogma. The other quotes develop in greater detail the “principles of Milesian naturalism.” Quotes 2 and 3 point to a cosmic and evolutionary development i.e. an unfolding of the universe as a whole, which occurred in accordance with patterns similar to those found in the universe today, and an evolution of life— including human life—from the sea to the land, implied by the of gills in fetuses, amphibian life, and the idea that ontogeny (individual development) repeats phylogeny (species development). Quote 4 suggests the idea of mathematical order: the earth is a sphere and there is a specific mathematical structure to the cosmic bodies, implied by the rounded horizon and the patterns of astronomical movements. Already, the Milesian physicist expects to be able to quantify natural patterns. Quote 5 introduces the concept of a unifying law: there is a single law governing the movements in the cosmos, implied by the cycles of the heavens, together with the cycles of daily, monthly, and annual life. (But there is an ambiguity here: is this a norm governing the world, or simply a regularity present in it? If it is a norm, who is the norm- giver?) Last but hardly least, quotes 2, 3 and 5 all suggest the idea of — that events (effects) come about as determined by a set of antecedent physical events (causes) operating according to laws or regular patterns, implied by the realization that things in nature occur “in accordance with necessity.” This introduces the idea of nature as not merely displaying recurrent patterns—which might or might not recur in the future—but as a system of causal relations, and natural laws identifying or describing those relations, an objective physical order. How does the world work, according to Anaximander? By one set of events, leading to others, shaping and forming according to patterns over time. The world is not subject to the whims of gods or magic or mere chance. The universe is not only materially one, but law-governed. It is a kosmos—a rational and beautiful world-order—not a chaos. This is a picture of the universe which, in many of its most basic features, is very like the modern scientific picture of the universe, particularly if it is contrasted to the pre-philosophical, mythical- religious picture of divine forces and agents. The Milesian picture was developed by the Atomists, so that it even more closely resembled that of modern science. 6

Anaximenes The third and last of the known leaders of the Milesian school was Anaximenes (c. 570-500 BC), who distinguished the planets (“wanderers”) and the fixed stars in his model of the universe, and explained extraordinary events such as lightning and the rainbow as the effect of natural causes, rather than as manifestations of Zeus or the goddess Iris. Anaximenes introduced the doctrine that air (aer) is the underlying elementary substance, and that all things are formed by it, depending on the extent to which it is rarefied or condensed: “The form of air is the following: when dissolved into what is finer, it becomes fire, winds when then condensed. Cloud results from air when it becomes denser, and water when this happens to a greater degree. Condensed still more, it becomes earth; at the densest stage, stones.” Anaximenes’ aer might be conceived of as being composed of more (denser) or less (finer) particles; in addition, his theory suggests that natural science should not merely describe the patterns of natural change, but explain why they occur in terms of the underlying causal mechanisms. These ideas be developed by the Atomists.

Compare the “5 Principles of Milesian Naturalism” with the scientific picture of the universe today. How are they alike? How different? Is this basically = your conception of the universe? If not, how do they differ?